Topic 6: Generators and Motors

Science 9 with Mrs M

Please take off your hats and hoods

Generating Power

• Most of our power comes from large power plants that convert mechanical energy into electrical energy

• Remember that question, “why are turbines so important?” We will answer that!

Topic 6 Generators and Motors

Power Plant Turbine -> Generator

• The turbine provides enough force to turn the generator’s coil of wires

Topic 6 Generators and Motors

Electric Generator

• Device that converts mechanical energy into electric energy

Topic 6 Generators and Motors NOTES

Generators

• Electricity and Magnetism are related

Topic 6 Generators and Motors NOTES

N S

Electricity and Magnetism are Related

Topic 6 Generators and Motors NOTES

How do we know?

• Compass needle turns when near electric field• With more electricity there is a stronger

needle deflection = stronger magnetic field

Topic 6 Generators and Motors NOTES

Topic 6 Generators and Motors NOTES

• Reverse the electric current and you reverse the direction of the magnetic field

• Stop the current = stop the magnetic field

Electromagnet

• When current is passed through a coil of wire wrapped around an iron rod an electromagnet is created

• North and south poles form on either end of the wire

• More coils = stronger magnet

Topic 6 Generators and Motors NOTES

Topic 6 Generators and Motors

Electromagnet from a soft iron core that becomes magnetic when current flows

Magnetized Material

Water has a dipole (North and South)Alignment of “poles” is similar to the alignment of charges.

Topic 6 Generators and Motors

MRI works on this principle

• (Magnetic Resonance Imaging)

Topic 6 Generators and Motors

Earth has a magnetic field

The human heart’s electrical impulses create a magnetic field

Example of an electromagnet:Maglev Trains

Links

• Using iron filings to observe field of solenoid https://www.youtube.com/watch?v=CZKNl9WBIk4

• melt metal with magnets https://www.youtube.com/watch?v=8i2OVqWo9s0

• Make a Magnetic Field https://www.youtube.com/watch?v=j8XNHlV6Qxg

Topic 6 Generators and Motors

Question:

• How are electricity and magnetism related?

Topic 6 Generators and Motors

How are electricity and magnetism related?

• Electricity and magnetism related because flowing electrons produce a magnetic field.

• Electricity and magnetism are ALSO related because spinning magnets can produce electricity.

Topic 6 Generators and Motors

Electricity and magnetism are related:flowing electrons produce a magnetic fieldspinning magnets can produce electricity

• https://www.youtube.com/watch?v=d_aTC0iKO68

• Motor: – electricity -> mechanical energy

• Generator: – magnet -> mechanical force -> electricity

Topic 6 Generators and Motors

• Motor: – electricity -> mechanical energy

• Generator: – magnet -> mechanical force -> electricity

AC Generators

- External force rotates the coil- Coil of wire rotates inside of a stationary magnetic field- Most generators use electromagnets instead of permanent magnets- As coil’s wires rotate inside the field, electrons move

Topic 6 Generators and Motors

AC: Alternating Current

• AC generators produce electricity that changes directions

• After one half-rotation of the coil, each side passes near the opposite pole of the magnet, and the electrons move in the opposite direction

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Benefits of AC current

• Easy to increase/decrease the voltage• This helps set up voltage for power line

transmission (more in Topic 7)

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DC Generators

• Current in only one direction

Topic 6 Generators and Motors

Electric Motors

• Convert electrical energy to mechanical energy

Topic 6 Generators and Motors

Exploratory Stations

• Generator• Motor• Electromagnets• Piezoelectric crystal• Bar magnet’s field lines

Topic 6 Generators and Motors