Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two...

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Magnets and Magnetic Fields Magnets • Magnets attract iron-containing objects. • Magnets have two distinct poles called the north pole and the south pole. These names are derived from a magnet’s behavior on Earth. • Like poles of magnets repel each other; unlike poles attract each other.

Transcript of Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two...

Page 1: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnets and Magnetic Fields

Magnets

• Magnets attract iron-containing objects.

• Magnets have two distinct poles called the north pole and the south pole. These names are derived from a magnet’s behavior on Earth.

• Like poles of magnets repel each other; unlike poles attract each other.

Page 2: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnets and Magnetic Fields

Magnetic Domains• Magnetic Domain

A region composed of a group of atoms whose magnetic fields are aligned in the same direction is called a magnetic domain.

• Some materials can be made into permanent magnets.– Soft magnetic materials (for example iron) are

easily magnetized but tend to lose their magnetism easily.

– Hard magnetic materials (for example nickel) tend to retain their magnetism.

Page 3: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnets and Magnetic Fields

Magnetic Fields

• A magnetic field is a region in which a magnetic force can be detected.

• Magnetic field lines can be drawn with the aid of a compass.

Page 4: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Bar Magnet

Magnets and Magnetic Fields

Page 5: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnets and Magnetic Fields

Magnetic Fields, continued

• Earth’s magnetic field is similar to that of a bar magnet.

• The magnetic south pole is near the Geographic North Pole. The magnetic north pole is near the Geographic South Pole.

• Magnetic declination is a measure of the difference between true north and north indicated by a compass.

Page 6: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Earth’s Magnetic Field

Magnets and Magnetic Fields

Page 7: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Current-Carrying Wire

• A long, straight, current-carrying wire has a cylindrical magnetic field.

• Compasses can be used to shown the direction of the magnetic field induced by the wire.

• The right-hand rule can be used to determine the direction of the magnetic field in a current-carrying wire.

Magnetism from Electricity

Page 8: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

The Right-Hand Rule

Magnetism from Electricity

Page 9: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Current-Carrying Wire

Magnetism from Electricity

Page 10: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Current-Carrying Wire

Magnetism from Electricity

Negative Current Positive CurrentZero Current

Page 11: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Current Loop

• Solenoids produce a strong magnetic field by combining several loops.

• A solenoid is a long, helically wound coil of insulated wire.

Magnetism from Electricity

Page 12: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Charged Particles in a Magnetic Field

• A charge moving through a magnetic field experiences a force proportional to the charge, velocity, and the magnetic field.

B F

magnetic

qv

magnetic field = magnetic force on a charged particle

(magnitude of charge)(speed of charge)

Page 13: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Charged Particles in a Magnetic Field, continued• The direction of the magnetic force on a moving

charge is always perpendicular to both the magnetic field and the velocity of the charge.

• An alternative right-hand rule can be used to find the direction of the magnetic force.

• A charge moving through a magnetic field follows a circular path.

Magnetic Force

Page 14: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Alternative Right-Hand Rule: Force on a Moving Charge

Magnetic Force

Page 15: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem

Particle in a Magnetic Field

A proton moving east experiences a force of 8.8 10–19 N upward due to the Earth’s magnetic field.At this location, the field has a magnitude of 5.5 10–5 T to the north. Find the speed of the particle.

Page 16: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem, continued

Particle in a Magnetic Field

Given:

q = 1.60 10–19 C

B = 5.5 10–5 T

Fmagnetic = 8.8 10–19 N

Unknown:

v = ?

Page 17: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem, continued

Particle in a Magnetic Field

Use the definition of magnetic field strength. Rearrange to solve for v.

–19

–19 –5

5

8.8 19 N

(1.60 19 )(5.5 10 )

1.0 10 m/s

magnetic

magnetic

FB

qv

Fv

qB

v

Page 18: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Magnetic Force on a Current-Carrying Conductor• A current-carrying wire in an external magnetic field

undergoes a magnetic force.

• The force on a current-carrying conductor perpendicular to a magnetic field is given by:

magnitude of magnetic force = (magnitude of magnetic field) (current) (length of conductor within B)

Page 19: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Force on a Current-Carrying Wire in a Magnetic Field

Magnetic Force

Page 20: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Magnetic Force on a Current-Carrying Conductor, continued• Two parallel current-carrying wires exert a force on

one another that are equal in magnitude and opposite in direction.

• If the currents are in the same direction, the two wires attract one another.

• If the currents are in opposite direction, the wires repel one another.

• Loudspeakers use magnetic force to produce sound.

Page 21: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Force Between Parallel Conducting Wires

Magnetic Force

Page 22: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem

Force on a Current-Carrying Conductor

A wire 36 m long carries a current of 22 A from east to west. If the magnetic force on the wire due to Earth’s magnetic field is downward (toward Earth) and has a magnitude of 4.0 10–2 N, find the magnitude and direction of the magnetic field at this location.

Page 23: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem, continued

Force on a Current-Carrying Conductor

Given:

I = 22 A

Fmagnetic = 4.0 10–2 N

Unknown:

B = ?

Page 24: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem, continued

Force on a Current-Carrying ConductorUse the equation for the force on a current-carrying conductor perpendicular to a magnetic field.

Rearrange to solve for B.

Page 25: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Force

Sample Problem, continued

Force on a Current-Carrying Conductor

Using the right-hand rule to find the direction of B, face north with your thumb pointing to the west (in the direction of the current) and the palm of your hand down (in the direction of the force). Your fingers point north. Thus, Earth’s magnetic field is from south to north.

Page 26: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice

1. Which of the following statements best describes the domains in unmagnetized iron?

A. There are no domains.

B. There are domains, but the domains are smaller than in magnetized iron.

C. There are domains, but the domains are oriented randomly.

D. There are domains, but the domains are not magnetized.

Page 27: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

1. Which of the following statements best describes the domains in unmagnetized iron?

A. There are no domains.

B. There are domains, but the domains are smaller than in magnetized iron.

C. There are domains, but the domains are oriented randomly.

D. There are domains, but the domains are not magnetized.

Page 28: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

2. Which of the following statements is most correct?F. The north pole of a freely rotating magnet points north because the magnetic pole near the geographic North Pole is like the north pole of a magnet.G. The north pole of a freely rotating magnet points north because the magnetic pole near the geographic North Pole is like the south pole of a magnet.H. The north pole of a freely rotating magnet points south because the magnetic pole near the geographic South Pole is like the north pole of a magnet.J. The north pole of a freely rotating magnet points south because the magnetic pole near the geographic South Pole is like the south pole of a magnet.

Page 29: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

2. Which of the following statements is most correct?F. The north pole of a freely rotating magnet points north because the magnetic pole near the geographic North Pole is like the north pole of a magnet.G. The north pole of a freely rotating magnet points north because the magnetic pole near the geographic North Pole is like the south pole of a magnet.H. The north pole of a freely rotating magnet points south because the magnetic pole near the geographic South Pole is like the north pole of a magnet.J. The north pole of a freely rotating magnet points south because the magnetic pole near the geographic South Pole is like the south pole of a magnet.

Page 30: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

3. If you are standing at Earth’s magnetic north pole and holding a bar magnet that is free to rotate in three dimensions, which direction will the south pole of the magnet point?

A. straight up

B. straight down

C. parallel to the ground, toward the north

D. parallel to the ground, toward the south

Page 31: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

3. If you are standing at Earth’s magnetic north pole and holding a bar magnet that is free to rotate in three dimensions, which direction will the south pole of the magnet point?

A. straight up

B. straight down

C. parallel to the ground, toward the north

D. parallel to the ground, toward the south

Page 32: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

4. How can you increase the strength of a magnetic field inside a solenoid?

F. increase the number of coils per unit length

G. increase the current

H. place an iron rod inside the solenoid

J. all of the above

Page 33: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

4. How can you increase the strength of a magnetic field inside a solenoid?

F. increase the number of coils per unit length

G. increase the current

H. place an iron rod inside the solenoid

J. all of the above

Page 34: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

5. How will the electron move once it passes into the magnetic field?A. It will curve to the right and then continue moving in a straight line to the right.B. It will curve to the left and then continue moving in a straight line to the left.C. It will move in a clockwise circle.D. It will move in a counterclockwise circle.

Page 35: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

5. How will the electron move once it passes into the magnetic field?A. It will curve to the right and then continue moving in a straight line to the right.B. It will curve to the left and then continue moving in a straight line to the left.C. It will move in a clockwise circle.D. It will move in a counterclockwise circle.

Page 36: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

6. What will be the magnitude of the force on the electron once it passes into the magnetic field?

F. qvB

G. –qvB

H. qB/v

J.

Page 37: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

6. What will be the magnitude of the force on the electron once it passes into the magnetic field?

F. qvB

G. –qvB

H. qB/v

J.

Page 38: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

7. An alpha particle (q = 3.2 10–19 C) moves at a speed of 2.5 106 m/s perpendicular to a magnetic field of strength 2.0 10–4 T. What is the magnitude of the magnetic force on the particle?

A. 1.6 10–16 N

B. –1.6 10–16 N

C. 4.0 10–9 N

D. zero

Page 39: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

7. An alpha particle (q = 3.2 10–19 C) moves at a speed of 2.5 106 m/s perpendicular to a magnetic field of strength 2.0 10–4 T. What is the magnitude of the magnetic force on the particle?

A. 1.6 10–16 N

B. –1.6 10–16 N

C. 4.0 10–9 N

D. zero

Page 40: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

Use the passage below to answer questions 8–9.A wire 25 cm long carries a 12 A current from east to west. Earth’s magnetic field at the wire’s location has a magnitude of 4.8 10–5 T and is directed from south to north.

8. What is the magnitude of the magnetic force on the wire?F. 2.3 10–5 NG. 1.4 10–4 NH. 2.3 10–3 NJ. 1.4 10–2 N

Page 41: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

Use the passage below to answer questions 8–9.A wire 25 cm long carries a 12 A current from east to west. Earth’s magnetic field at the wire’s location has a magnitude of 4.8 10–5 T and is directed from south to north.

8. What is the magnitude of the magnetic force on the wire?F. 2.3 10–5 NG. 1.4 10–4 NH. 2.3 10–3 NJ. 1.4 10–2 N

Page 42: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

Use the passage below to answer questions 8–9.A wire 25 cm long carries a 12 A current from east to west. Earth’s magnetic field at the wire’s location has a magnitude of 4.8 10–5 T and is directed from south to north.

9. What is the direction of the magnetic force on the wire?A. northB. southC. up, away from EarthD. down, toward Earth

Page 43: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

Use the passage below to answer questions 8–9.A wire 25 cm long carries a 12 A current from east to west. Earth’s magnetic field at the wire’s location has a magnitude of 4.8 10–5 T and is directed from south to north.

9. What is the direction of the magnetic force on the wire?A. northB. southC. up, away from EarthD. down, toward Earth

Page 44: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

10. What is the direction of the magnetic field B1 at the location of wire 2?

F. to the left

G. to the right

H. into the page

J. out of the page

Page 45: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

10. What is the direction of the magnetic field B1 at the location of wire 2?

F. to the left

G. to the right

H. into the page

J. out of the page

Page 46: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

11. What is the direction of the force on wire 2 as a result of B1?

A. to the left

B. to the right

C. into the page

D. out of the page

Page 47: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

11. What is the direction of the force on wire 2 as a result of B1?

A. to the left

B. to the right

C. into the page

D. out of the page

Page 48: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

I 2 2 2B

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

12. What is the magnitude of the magnetic force on wire 2?

Page 49: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

1 1 1

1 1 2

2 2 2

1 2 2

I

I

I

I

B

B

B

B

• Wire 1 carries current I1 and creates magnetic field B1.

• Wire 2 carries current I2 and creates magnetic field B2.

12. What is the magnitude of the magnetic force on wire 2?

Page 50: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response

13. Sketch the magnetic field lines around a bar magnet.

Page 51: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

13. Sketch the magnetic field lines around a bar magnet.

Answer:

Page 52: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

14. Describe how to use the right-hand rule to determine the direction of a magnetic field around a current-carrying wire.

Page 53: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

14. Describe how to use the right-hand rule to determine the direction of a magnetic field around a current-carrying wire.

Answer: Imagine wrapping the fingers of your right hand around the wire and pointing your thumb in the direction of the current. The magnetic field lines form concentric circles that are centered on the wire and curve in the same direction as your fingers.

Page 54: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

15. Draw a diagram showing the path of a positively charged particle moving in the plane of a piece of paper if a uniform magnetic field is coming out of the page.

Page 55: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

15. Draw a diagram showing the path of a positively charged particle moving in the plane of a piece of paper if a uniform magnetic field is coming out of the page.

Answer:

Page 56: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Magnetic Field of a Current Loop

Magnetism from Electricity

Page 57: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Electromagnetic Induction

• Electromagnetic induction is the process of creating a current in a circuit by a changing magnetic field.

• A change in the magnetic flux through a conductor induces an electric current in the conductor.

• The separation of charges by the magnetic force induces an emf.

Page 58: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Induction in a Circuit Loop

Electricity from Magnetism

Page 59: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Electromagnetic Induction, continued

• The angle between a magnetic field and a circuit affects induction.

• A change in the number of magnetic field lines induces a current.

Page 60: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Characteristics of Induced Current• Lenz’s Law

The magnetic field of the induced current is in a direction to produce a field that opposes the change causing it.

• Note: the induced current does not oppose the applied field, but rather the change in the applied field.

Page 61: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Characteristics of Induced Current, continued• The magnitude of the induced emf can be predicted

by Faraday’s law of magnetic induction.

• Faraday’s Law of Magnetic Induction

average induced emf = –the number of loops in the circuit

the time rate of change in the magnetic flux

– Memf Nt

• The magnetic flux is given by M = ABcos

Page 62: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem

Induced emf and Current

A coil with 25 turns of wire is wrapped around a hollow tube with an area of 1.8 m2. Each turn has the same area as the tube. A uniform magnetic field is applied at a right angle to the plane of the coil. If the field increases uniformly from 0.00 T to 0.55 T in 0.85 s, find the magnitude of the induced emf in the coil. If the resistance in the coil is 2.5 Ω, find the magnitude of the induced current in the coil.

Page 63: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current

1. Define

Given:

∆t = 0.85 s A = 1.8 m2 = 0.0º

N = 25 turns R = 2.5 Ω

Bi = 0.00 T = 0.00 V•s/m2

Bf = 0.55 T = 0.55 V•s/m2

Unknown:

emf = ?

I = ?

Page 64: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current1. Define, continued

Diagram: Show the coil before and after the change in the magnetic field.

Page 65: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current

2. Plan

Choose an equation or situation. Use Faraday’s law of magnetic induction to find the induced emf in the coil.

cos– –M

ABemf N N

t tSubstitute the induced emf into the definition of resistance to determine the induced current in the coil.

emf

IR

Page 66: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current

2. Plan, continued

Rearrange the equation to isolate the unknown. In this example, only the magnetic field strength changes with time. The other components (the coil area and the angle between the magnetic field and the coil) remain constant.

– cos

Bemf NA

t

Page 67: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current3. Calculate

Substitute the values into the equation and solve.

22

V•s0.55 – 0.00

m–(25)(1.8 m )(cos0.0º ) –29 V

(0.85 s)

–29 V–12 A

2.5 Ω

–29 V

–12 A

emf

I

emf

I

Page 68: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electricity from Magnetism

Sample Problem, continued

Induced emf and Current4. Evaluate

The induced emf, and therefore the induced current, is directed through the coil so that the magnetic field produced by the induced current opposes the change in the applied magnetic field. For the diagram shown on the previous page, the induced magnetic field is directed to the right and the current that produces it is directed from left to right through the resistor.

Page 69: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Generators, Motors, and Mutual Inductance

Generators and Alternating Current• A generator is a machine that converts mechanical

energy into electrical energy.

• Generators use induction to convert mechanical energy into electrical energy.

• A generator produces a continuously changing emf.

Page 70: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Induction of an emf in an AC Generator

Generators, Motors, and Mutual Inductance

Page 71: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Generators, Motors, and Mutual Inductance

Generators and Alternating Current, continued

• Alternating current is an electric current that changes direction at regular intervals.

• Alternating current can be converted to direct current by using a device called a commutator to change the direction of the current.

Page 72: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Generators, Motors, and Mutual Inductance

Motors

• Motors are machines that convert electrical energy to mechanical energy.

• Motors use an arrangement similar to that of generators.

• Back emf is the emf induced in a motor’s coil that tends to reduce the current in the coil of a motor.

Page 73: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Generators, Motors, and Mutual Inductance

Mutual Inductance

• The ability of one circuit to induce an emf in a nearby circuit in the presence of a changing current is called mutual inductance.

• In terms of changing primary current, Faraday’s law is given by the following equation, where M is the mutual inductance:

– –M I

emf N Mt t

Page 74: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Objectives

• Distinguish between rms values and maximum values of current and potential difference.

• Solve problems involving rms and maximum values of current and emf for ac circuits.

• Apply the transformer equation to solve problems involving step-up and step-down transformers.

Page 75: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Effective Current

• The root-mean-square (rms) current of a circuit is the value of alternating current that gives the same heating effect that the corresponding value of direct current does.

• rms Current

maxmax0.707

2rms

II I

Page 76: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Effective Current, continued

• The rms current and rms emf in an ac circuit are important measures of the characteristics of an ac circuit.

• Resistance influences current in an ac circuit.

Page 77: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Sample Problem

rms Current and emf

A generator with a maximum output emf of 205 V is connected to a 115 Ω resistor. Calculate the rms potential difference. Find the rms current through the resistor. Find the maximum ac current in the circuit.

1. DefineGiven:

∆Vrms = 205 VR = 115 ΩUnknown:

∆Vrms = ? Irms = ? Imax = ?

Page 78: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Sample Problem, continued

rms Current and emf2. Plan

Choose an equation or situation. Use the equation for the rms potential difference to find ∆Vrms.

∆Vrms = 0.707 ∆Vmax

Rearrange the definition for resistance to calculate Irms.

rmsrms

VI

R

Use the equation for rms current to find Irms.

Irms = 0.707 Imax

Page 79: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Sample Problem, continued

rms Current and emf2. Plan, continued

Rearrange the equation to isolate the unknown. Rearrange the equation relating rms current to maximum current so that maximum current is calculated.

max 0.707rmsI

I

Page 80: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Sample Problem, continued

rms Current and emf3. Calculate

Substitute the values into the equation and solve.

max

(0.707)(205 V) 145 V

145 V1.26 A

115 Ω1.26 A

1.78 A0.707

rms

rms

V

I

I

4. Evaluate The rms values for emf and current are a little more than two-thirds the maximum values, as expected.

Page 81: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Transformers

• A transformer is a device that increases or decreases the emf of alternating current.

• The relationship between the input and output emf is given by the transformer equation.

22 1

1

induced emf in secondary =

number of turns in secondaryapplied emf in primary

number of turns in primary

NV V

N

Page 82: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

AC Circuits and Transformers

Transformers, continued

• The transformer equation assumes that no power is lost between the primary and secondary coils. However, real transformers are not perfectly efficient.

• Real transformers typically have efficiencies ranging from 90% to 99%.

• The ignition coil in a gasoline engine is a transformer.

Page 83: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

A Step-Up Transformer in an Auto Ignition System

AC Circuits and Transformers

Page 84: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Waves

Propagation of Electromagnetic Waves• Electromagnetic waves travel at the speed of light

and are associated with oscillating, perpendicular electric and magnetic fields.

• Electromagnetic waves are transverse waves; that is, the direction of travel is perpendicular to the the direction of oscillating electric and magnetic fields.

• Electric and magnetic forces are aspects of a single force called the electromagnetic force.

Page 85: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Waves

Propagation of Electromagnetic Waves, continued• All electromagnetic waves are produced by

accelerating charges.

• Electromagnetic waves transfer energy. The energy of electromagnetic waves is stored in the waves’ oscillating electric and magnetic fields.

• Electromagnetic radiation is the transfer of energy associated with an electric and magnetic field. Electromagnetic radiation varies periodically and travels at the speed of light.

Page 86: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

The Sun at Different Wavelengths of Radiation

Electromagnetic Waves

Page 87: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Waves

Propagation of Electromagnetic Waves, continued• High-energy electromagnetic waves behave like

particles.

• An electromagnetic wave’s frequency makes the wave behave more like a particle. This notion is called the wave-particle duality.

• A photon is a unit or quantum of light. Photons can be thought of as particles of electromagnetic radiation that have zero mass and carry one quantum of energy.

Page 88: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Waves

The Electromagnetic Spectrum

• The electromagnetic spectrum ranges from very long radio waves to very short-wavelength gamma waves.

• The electromagnetic spectrum has a wide variety of applications and characteristics that cover a broad range of wavelengths and frequencies.

Page 89: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Electromagnetic Waves

The Electromagnetic Spectrum, continued• Radio Waves

– longest wavelengths– communications, tv

• Microwaves– 30 cm to 1 mm– radar, cell phones

• Infrared– 1 mm to 700 nm– heat, photography

• Visible light– 700 nm (red) to 400 nm

(violet)

• Ultraviolet– 400 nm to 60 nm– disinfection,

spectroscopy• X rays

– 60 nm to 10–4 nm– medicine, astronomy,

security screening• Gamma Rays

– less than 0.1 nm– cancer treatment,

astronomy

Page 90: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

The Electromagnetic Spectrum

Electromagnetic Waves

Page 91: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice

1. Which of the following equations correctly describes Faraday’s law of induction?

( tan ) –

( cos )

( cos ) –

( cos )

ABemf N

tAB

emf Nt

ABemf N

tAB

emf Mt

A.

B.

C.

D.

Page 92: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

1. Which of the following equations correctly describes Faraday’s law of induction?

( tan ) –

( cos )

( cos )

( co

–

s )

ABemf N

tAB

emf Nt

ABemf M

t

ABemf N

tC

D.

.

A.

B.

Page 93: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

2. For the coil shown at right, what must be done to induce a clockwise current?

F. Either move the north pole of a magnet down into the coil, or move the south pole of the magnet up and out of the coil.

G. Either move the south pole of a magnet down into the coil, or move the north pole of the magnet up and out of the coil.

H. Move either pole of the magnet down into the coil.

J. Move either pole of the magnet up and out of the coil.

Page 94: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

2. For the coil shown at right, what must be done to induce a clockwise current?

F. Either move the north pole of a magnet down into the coil, or move the south pole of the magnet up and out of the coil.

G. Either move the south pole of a magnet down into the coil, or move the north pole of the magnet up and out of the coil.

H. Move either pole of the magnet down into the coil.

J. Move either pole of the magnet up and out of the coil.

Page 95: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

3. Which of the following would not increase the emf produced by a generator?

A. rotating the generator coil faster

B. increasing the strength of the generator magnets

C. increasing the number of turns of wire in the coil

D. reducing the cross-sectional area of the coil

Page 96: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

3. Which of the following would not increase the emf produced by a generator?

A. rotating the generator coil faster

B. increasing the strength of the generator magnets

C. increasing the number of turns of wire in the coil

D. reducing the cross-sectional area of the coil

Page 97: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

4. By what factor do you multiply the maximum emf to calculate the rms emf for an alternating current?

2

2

1

21

2

F.

G.

H.

J.

Page 98: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

4. By what factor do you multiply the maximum emf to calculate the rms emf for an alternating current?

2

2

1

1

2

2

H.

F.

G.

J.

Page 99: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

5. Which of the following correctly describes the composition of an electromagnetic wave?A. a transverse electric wave and a magnetic transverse wave that are parallel and are moving in the same directionB. a transverse electric wave and a magnetic transverse wave that are perpendicular and are moving in the same directionC. a transverse electric wave and a magnetic transverse wave that are parallel and are moving at right angles to each otherD. a transverse electric wave and a magnetic transverse wave that are perpendicular and are moving at right angles to each other

Page 100: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

5. Which of the following correctly describes the composition of an electromagnetic wave?A. a transverse electric wave and a magnetic transverse wave that are parallel and are moving in the same directionB. a transverse electric wave and a magnetic transverse wave that are perpendicular and are moving in the same directionC. a transverse electric wave and a magnetic transverse wave that are parallel and are moving at right angles to each otherD. a transverse electric wave and a magnetic transverse wave that are perpendicular and are moving at right angles to each other

Page 101: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

6. A coil is moved out of a magnetic field in order to induce an emf. The wire of the coil is then rewound so that the area of the coil is increased by 1.5 times. Extra wire is used in the coil so that the number of turns is doubled. If the time in which the coil is removed from the field is reduced by half and the magnetic field strength remains unchanged, how many times greater is the new induced emf than the original induced emf ?F. 1.5 timesG. 2 timesH. 3 timesJ. 6 times

Page 102: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

6. A coil is moved out of a magnetic field in order to induce an emf. The wire of the coil is then rewound so that the area of the coil is increased by 1.5 times. Extra wire is used in the coil so that the number of turns is doubled. If the time in which the coil is removed from the field is reduced by half and the magnetic field strength remains unchanged, how many times greater is the new induced emf than the original induced emf ?F. 1.5 timesG. 2 timesH. 3 timesJ. 6 times

Page 103: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

7. From left to right, what are the types of the two transformers?A. Both are step-down transformers.B. Both are step-up transformers.C. One is a step-down transformer; and one is a step-up transformer.D. One is a step-up transformer; and one is a step-down transformer.

Use the passage below to answer questions 7–8.A pair of transformers is connected in series, as shown in the figure below.

Page 104: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

7. From left to right, what are the types of the two transformers?A. Both are step-down transformers.B. Both are step-up transformers.C. One is a step-down transformer; and one is a step-up transformer.D. One is a step-up transformer; and one is a step-down transformer.

Use the passage below to answer questions 7–8.A pair of transformers is connected in series, as shown in the figure below.

Page 105: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

8. What is the output potential difference from the secondary coil of the transformer on the right?

F. 400 V

G. 12 000 V

H. 160 000 V

J. 360 000 V

Use the passage below to answer questions 7–8.A pair of transformers is connected in series, as shown in the figure below.

Page 106: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

8. What is the output potential difference from the secondary coil of the transformer on the right?

F. 400 V

G. 12 000 V

H. 160 000 V

J. 360 000 V

Use the passage below to answer questions 7–8.A pair of transformers is connected in series, as shown in the figure below.

Page 107: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

9. What are the particles that can be used to describe electromagnetic radiation called?

A. electrons

B. magnetons

C. photons

D. protons

Page 108: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

9. What are the particles that can be used to describe electromagnetic radiation called?

A. electrons

B. magnetons

C. photons

D. protons

Page 109: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

10. The maximum values for the current and potential difference in an ac circuit are 3.5 A and 340 V, respectively. How much power is dissipated in this circuit?

F. 300 W

G. 600 W

H. 1200 W

J. 2400 W

Page 110: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Multiple Choice, continued

10. The maximum values for the current and potential difference in an ac circuit are 3.5 A and 340 V, respectively. How much power is dissipated in this circuit?

F. 300 W

G. 600 W

H. 1200 W

J. 2400 W

Page 111: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response

11. The alternating current through an electric toaster has a maximum value of 12.0 A. What is the rms value of this current?

Page 112: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

11. The alternating current through an electric toaster has a maximum value of 12.0 A. What is the rms value of this current?

Answer:

8.48 A

Page 113: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

12. What is the purpose of a commutator in an ac generator?

Page 114: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

12. What is the purpose of a commutator in an ac generator?

Answer:

It converts ac to a changing current in one direction only.

Page 115: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

13. How does the energy of one photon of an electromagnetic wave relate to the wave’s frequency?

Page 116: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

13. How does the energy of one photon of an electromagnetic wave relate to the wave’s frequency?

Answer:

The energy is directly proportional to the wave’s frequency (E = hf ).

Page 117: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

14. A transformer has 150 turns of wire on the primary coil and 75 000 turns on the secondary coil. If the input potential difference across the primary is 120 V, what is the output potential difference across the secondary?

Page 118: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Short Response, continued

14. A transformer has 150 turns of wire on the primary coil and 75 000 turns on the secondary coil. If the input potential difference across the primary is 120 V, what is the output potential difference across the secondary?

Answer:

6.0 104 V

Page 119: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response

15. Why is alternating current used for power transmission instead of direct current? Be sure to include power dissipation and electrical safety considerations in your answer.

Page 120: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

15. Answer:For electric power to be transferred over long distances without a large amount of power dissipation, the electric power must have a high potential difference and low current. However, to be safely used in homes, the potential difference must be lower than that used for long-distance power transmission. Because of induction, the potential difference and current of electricity can be transformed to higher or lower values, but the current must change continuously (alternate) for this to happen.

Page 121: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continuedBase your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

16. Why must the current enter the coil just as someone comes up to the table?

Page 122: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

16. Why must the current enter the coil just as someone comes up to the table?

Answer: The change in current in the coil will produce a changing magnetic field, which will induce a current in the ring. The induced current produces a magnetic field that interacts with the magnetic field from the coil, causing the ring to rise from the table.

Base your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

Page 123: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

17. Using Lenz’s law, explain why the ring flies upward when there is an increasing current in the coil?

Base your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

Page 124: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

17. Using Lenz’s law, explain why the ring flies upward when there is an increasing current in the coil?

Answer: According to Lenz’s law, the magnetic field induced in the ring must oppose the magnetic field that induces the current in the ring. The opposing fields cause the ring, which can move freely, to rise upward from the coil under the table’s surface.

Base your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

Page 125: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

18. Suppose the change in the magnetic field is 0.10 T/s. If the radius of the ring is 2.4 cm and the ring is assumed to consist of one turn of wire, what is the emf induced in the ring?

Base your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

Page 126: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Extended Response, continued

18. Suppose the change in the magnetic field is 0.10 T/s. If the radius of the ring is 2.4 cm and the ring is assumed to consist of one turn of wire, what is the emf induced in the ring?

Answer: 1.8 10–4 V

Base your answers to questions 16–18 on the information below.

A device at a carnival’s haunted house involves a metal ring that flies upward from a table when a patron passes near the table’s edge. The device consists of a photoelectric switch that activates the circuit when anyone walks in front of the switch and of a coil of wire into which a current is suddenly introduced when the switch is triggered.

Page 127: Magnets and Magnetic Fields Magnets Magnets attract iron-containing objects. Magnets have two distinct poles called the north pole and the south pole.

Ways of Inducing a Current in a Circuit

Electricity from Magnetism


Magnets have 2 poles (north and south) Like poles repel Unlike poles attract Magnets create a MAGNETIC FIELD around them.

Magnets have 2 poles (north and south) Like poles repel Unlike poles attract Magnets create a MAGNETIC FIELD around them.

12.1 - Light Poles Holophane Pole Standard Square or Round ...

12.1 - Light Poles Holophane Pole Standard Square or Round ...

Magnetism Web viewMagnetism All magnets have two poles: The North pole and the South pole. They are called so because if you hang a magnet by a thread, it will rotate so that the two

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Jumpstart to Primary Science - Admiralty Primary · Science Concepts •Magnets are made of iron that can attract iron and steel. •Has 2 poles –north and south poles. •Magnets

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Magnetism. Magnets, Magnetic Poles, and Magnetic Field Direction Magnets have two distinct types of poles; we refer to them as north and south.

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Magical Magnets by Vicki Broughton The opposite poles attract North pole to South pole. South pole to North pole.

Magical Magnets by Vicki Broughton The opposite poles attract North pole to South pole. South pole to North pole.

Drawing Magnetic Field Lines - National MagLab · Magnets have two poles; the fi eld lines spread out from the north pole and circle back around to the south pole. In this activity,

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Properties of magnets Magnet- material that can exert forces on magnets or other magnetic materials, like iron and steel. Poles- all magnets have 2- North.

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Chapter 20 Magnetism. Magnets The ends of a bar magnet are called poles Like poles repel and unlike poles attract Regardless of their shape, all magnets.

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Magnets and Electromagnetism Chapter Outline 1.Magnets, magnetic poles, and magnetic force. 2.Magnetic…

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ALL magnets have two poles NORTH seeking pole SOUTH seeking pole.

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Magnetic Fields and Forces Honors Physics. Facts about Magnetism Magnets have 2 poles (north and south) Like poles repel Unlike poles attract Magnets.

Magnetic Fields and Forces Honors Physics. Facts about Magnetism Magnets have 2 poles (north and south) Like poles repel Unlike poles attract Magnets.

What happens to magnets when like poles are placed together? They repel.

What happens to magnets when like poles are placed together? They repel.

Magnetostatics. Magnets and Magnetic Fields Magnets have two ends – poles – called north and south. Like poles repel; unlike poles attract.

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Chapter 20 Magnetism. 20.1 Magnets and Magnetic Fields Magnets have two ends – poles – called north and south. Like poles repel; unlike poles attract.

Chapter 20 Magnetism. 20.1 Magnets and Magnetic Fields Magnets have two ends – poles – called north and south. Like poles repel; unlike poles attract.

PRESENTACIÓN BAMBU INGLES - Gaviota Simbac de prezentare Bambu... · BAMBU Placing the poles in the base poles: • Put the pole in the base pole. Note: The poles at the base can

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Pole 10350 SPEC SECTION FLAGPOLES Industries - IPI Poles

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Magnetism. All of us are familiar with magnets. In a magnet we have magnetic poles – the north and the south pole. All of us are familiar with magnets.

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The law of magnets Like poles repel unlike poles attract TRIPLE ONLY.

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