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CircuitsLesson 01: ChargeLesson 02: Circuit DiagramsLesson 03: Series CircuitsLesson 04: Parallel Circuits

Which Circuit?Lesson 05: ResistanceLesson 06: Voltage, Current and ResistanceLesson 07: Voltage, Current and ResistanceLesson 08: Revision


Glossary

ammeter – A device used to measure current. ampere – The unit used to measure current. Its symbol is A. battery – The scientific word for two or more cells that are joined together. cell – A chemical source of voltage. The chemicals inside this device react and electrons are pushed out into

the circuit. circuit – A complete path that current can travel along. current – The rate of flow of electric charge in a circuit. It is measured in amperes (A). electron flow – The movement of negatively-charged electrons from a negative terminal around a circuit. parallel circuit – A complete circuit that branches into two or more paths. potential difference – The scientific name for voltage, measured in volts (V). Measured across a

component, it is the difference in electrical potential energy between the two sides of the component. series circuit – A complete circuit in which components are wired one after the other in a continuous loop. volt – The unit used to measure potential difference (voltage). Its symbol is V. voltmeter – A device used to measure potential difference (voltage). voltage – Another name for potential difference. For a cell, it is the amount of energy that the cell gives to

each electron pushed out into the circuit. diode – A component that allows current to flow in one direction only. light dependent resistor – A component whose resistance changes in response to light intensity. ohm – The unit of electrical resistance, named after

Georg Ohm. Ohm’s law – Formula used to relate current, voltage and resistance, if the temperature remains constant. R

= V/I. resistance – The opposition to the flow of charge. resistor – A component that opposes the flow of charge. thermistor – A component whose resistance changes in response to temperature. variable resistor – A component whose resistance can be adjusted to vary the amount of current.


Double Award Syllabus: explain why a series or parallel circuit is more appropriate for

particular applications, including domestic lighting (P2.10) understand that the current in a series circuit depends on the

applied voltage and the number and nature of other components (P2.11)

describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can be investigated experimentally (P2.12)

describe the qualitative effect of changing resistance on the current in a circuit (P2.13)

describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature (P2.14)

recall and use the relationship between voltage, current and resistance:

voltage = current × resistance V = I × R (P2.15) understand that current is the rate of flow of charge (P2.16) recall and use the relationship between charge, current and time:

charge = current × time Q = I × t (P2.17) recall that electric current in solid metallic conductors is a

flow of negatively charged electrons (P2.18).


Separate Science Syllabus

Energy and Potential Difference in Circuits explain why a series or parallel circuit is more appropriate for particular applications, including domestic

lighting understand that the current in a series circuit depends on the applied voltage and the number and nature of

other components describe how current varies with voltage in wires, resistors, metal filament lamps and diodes, and how this can

be investigated experimentally describe the qualitative effect of changing resistance on the current in a circuit describe the qualitative variation of resistance of LDRs with illumination and of thermistors with temperature recall and use the relationship between voltage, current and resistance:

voltage = current × resistance V = I × R

understand that current is the rate of flow of charge recall and use the relationship between charge, current and time :

charge = current × time Q = I × t

recall that electric current in solid metallic conductors is a flow of negatively charged electrons recall that:

voltage is the energy transferred per unit charge passed the volt is a joule per coulomb

Electric charge identify materials which are electrical conductors or insulators, including metals and plastics recall that insulating materials can be charged by friction explain that positive and negative electrostatic charges are produced on materials by the loss and

gain of electrons recall that there are forces of attraction between unlike charges and forces of repulsion between

like charges explain electrostatic phenomena in terms of the movement of electrons recall the potential dangers of electrostatic charges, e.g. when fuelling aircraft and tankers recall some uses of electrostatic charges, e.g. in photocopiers and inkjet printers


Charge 19/04/23

Aim: To generate a charge To calculate chargeStarter: Where is the static electricity in the picture?


What did Benjamin Franklin do?


How is Static Charge Generated? How can you generate static charge?

Around the outside of an atom are electrons, which have a negative charge.

The nucleus at the centre of an atom contains protons, which have a positive charge.


Charging materials

Video


Investigating pairs of chargesSeparate Science


Separate ScienceCharge Insulators can be charged by friction If a material is turned positive then electrons have

been lost if the material becomes negative the electrons have

been gained Like charges repel Different charges attract


Demos Water Paper


Experimenting with static charge


Charge The number of electrons (or other ions) Symbol: Q Units: coulomb (C) Charge on 1 electron = 1.6 × 10-19 C

Charles–Augustin de Coulomb (1736-1806)

Charge = current x time

(in C) (in A) (in s)

Q

tI

Q u I t


Example questions

Charge (C) Current (A) Time (s)

5 2

0.4 1

20 0.5

50 250

3 60

1) A circuit is switched on for 30s with a current of 3A. How much charge flowed?

2) During electrolysis 6A was passed through some copper chloride and a charge of 1200C flowed. How long was the experiment on for?

3) A bed lamp is switched on for 10 minutes. It works on a current of 0.5A. How much charge flowed?


A build up of static charge when refuelling a plane could cause an explosion.

The wire provides a path for electricity to flow along, and so prevents the build up of any potentially dangerous static charge.

This can be prevented by joining the delivery tanker and the fuel tank electrically with a metal wire.

metal wire

How are planes refuelled safely?Separate Science

Petrol Pump


Separate ScienceDangers

Sparks are caused by electrons moving When a plane is refuelling you can get a build up of

electrostatic charges


How does a photocopier work?Separate Science


What happens in a photocopier?Separate Science


Inkjet printer

•The ink droplets are charged as they thrust against the nozzle•The droplets are deflected as they pass between two electrically

charged plates•The amount of charge, i.e. the size and direction of the voltage, on

the plates keeps changing to drive each droplet to the right place on your paper

•What charge will the droplets deflected upwardly have? Why?•They will be negatively charged, because -ve charges are attracted

by the positive plate at the top and repelled by the negative plate at the bottom.

A4 paper

Fine nozzle

Positive plate

Negative plate

Separate Science


How does spray painting cars work?Separate Science


How does static charge reduce pollution?

A precipitator in the chimney of a power station uses static electricity to filter smoke particles from waste gases.

The smoke particles pass through a charged grid and pick up a negative charge.

positively- charged metal plates

metal grid at a high voltage

smoke particles

They are then attracted to the positively-charged collecting plates.

The smoke particles lose their charge and fall back down the chimney, so the waste gases emitted are free of polluting smoke.

Separate Science


Separate ScienceUses Electrostatic charges are used in photocopiers, inkjet printers,

spray paints and precipitators


Static electricity – useful or a problem?Separate Science


‘Van de Graaff’ generator

Brainiac


Anagrams


Multiple-choice quiz


Charge recapAim To generate a charge To calculate charge


Circuit Diagrams 19/04/23

Aim Use circuit symbols Understand circuit diagrams

Starter: True or False (back of books)

1)1) Voltage can also be called potential difference.Voltage can also be called potential difference.

2)2) There must be a gap in a circuit for a current to flow.There must be a gap in a circuit for a current to flow.

3)3) Electrons carry energy round a circuit.Electrons carry energy round a circuit.

4)4) A light bulb transfers electrical energy into heat and light.A light bulb transfers electrical energy into heat and light.

5)5) Current is measured in volts.Current is measured in volts.

6)6) If more electrons start flowing round a circuit the current gets If more electrons start flowing round a circuit the current gets smaller smaller


----

-- - -

-

----

- --


Circuit symbols


Circuit Symbols

Wire

Connected Wire

Non connecting wire

Cell

Battery

Power supply

Switch

Voltmeter

Ammeter

Motor

Fuse

Buzzer

Diode

Bulb

Resistor

Thermistor

Variable

Resistor

Light Dependant Resistor (LDR)


Could you draw the circuit?


Why Use Circuit Diagrams?


Types of Circuits


----

-- - -

-

----

- --If there is only one path for thecurrent we say the bulbs areconnected in SERIES.


----

--

-

---

-

-

-

- --Here the current has tworoutes.

Any circuit with more than oneroute means that the bulbs are

connected in PARALLEL.


----

-- - -

-

----

- --

- ---

If a wire is connected aroundthe bulb all the current willbypass the bulb and it goes out

We call this a SHORT CIRCUIT


Which circuit diagram?


Building Circuits Practise 1 Power Pack set at 3V 2 Bulbs 1 Switch 1 Motor 1 Buzzer 6 Wires 1 Voltmeter 2 Croc Clips

Draw each circuit first When Connecting Parallel circuits connect up the

series section first. make sure you have that right. then add at the parallel branch. Make sure they connect where the “blobs” are in

the circuit. Measure the Voltage across each component and

the power pack and note it down on your circuit diagram

The buzzers need to be connected the correct way


M

M

M

1

65

2 3

4


Circuit Diagrams recap

Aim Use circuit symbols Understand circuit diagrams

Homework


Battery

Power supply

Switch

Voltmeter

Ammeter

Diode

Resistor

Thermistor

Variable

Resistor


Quiz:

Series Circuits 19/04/23

Aims:•To define Current, Voltage and Resistance•To investigate current and voltage in series circuits

Power supply

Voltmeter

Diode

Thermistor


Quiz:


Potential Difference The push on electrons

in a circuit. so bigger push, faster

electrons, more current, brighter bulb

Symbol: V Units: volts (V) A.k.a. Voltage

Alessandro Giuseppe Antonio Anastasio Volta (1745-1827)


Current

The number of electrons flowing past a point in a circuit.

So faster electrons or more electrons, bigger current, brighter bulb

Conventional Current flows from positive to negative however electrons are negative so they really flow from negative to positive

Symbol: I Units: ampere (A)

(ampere = amps)

André-Marie Ampère (1775-1836)


Representing current direction


Resistance How hard it is for a

current to flow through a material.

So bigger resistance but same voltage gives a smaller current

Symbol: R Units: ohms (Ω)

George Simon Ohm (1789-1854)


Analogy 1: Cross Country Run

Copy down the sketch on the board and annotate it.

USE MOST OF A PAGE LEAVE SPACE FOR FURTHER

ADDITIONS NEXT LESSON

PE Teachers = Voltage

Pupils = electrons

Rate of pupils moving = Current

Other Teachers counting Pupils = Ammeter

Obstacles = Resistances (e.g. Resistors, bulbs, motors ...)

Short cuts = Short circuits


Experiment Follow the experiment sheet DO NOT WRITE ON THE SHEET


Series circuits – experiment

NOTE: Voltage Reading on 3 bulbs, 1 battery is wrong should be 0.67 V


Current in a Series Circuit Copy the circuit into your books Measure the current at points A1, A2 and A3

Write down your readings: What has happened to the current?

A 1 A 3

A2

• Electrons are never ever used up• So, the current is the same in all parts of a series circuit.

A1 = A2 = A3

A1 = A2 = A3 =


• In a series circuit, the voltage supplied by the battery is shared by the components.

• So, the sum of the voltage across the components equals the battery voltage.

V1

V3V2

Voltage in a Series Circuit

V1 = V2 + V3

Copy the circuit into your books Measure the voltage at points V1, V2 and V3

Write down your readings:

V1 =

V2 =

V3 =


Series Circuits recap

Aims:•To define Current, Voltage and Resistance•To investigate current and voltage in series circuits


Parallel Circuits 19/04/23

Aims:•To experimentally establish the behaviour of current and voltage in parallel circuits

Starter: (back of books)Which is the odd one out?

A B C D


Potential Difference Across Cells

Batteries are made of multiple cells For instance a car battery has at least 6 To work out the voltage of the battery just

add together the voltage of the cells.

Q: What is the total potential difference of 2 x 1.5V batteries in series?A: V = 1.5 + 1.5 = 3 V


Work out the Potential Difference of the Following (don’t forget positive and negative ends)

a)

c) d)

b)

1.5+1.5+1.5 = 4.5V

1.5+1.5-1.5-1.5 = 0V1.5+1.5-1.5 = 1.5V

1.5-1.5 = 0V


Experiment Follow the experiment sheet DO NOT WRITE ON THE SHEET


Parallel Circuits – Experiment


•The electrons must choose which way to go•So, the current is not the same in all parts of a parallel

circuit.

A 1 A 6

A3

A2

Current in a Parallel Circuit Copy the circuit into your books Measure the current at points A1, A2 and A3

Write down your readings: What has happened to the current?

A1 = A2 + A3 A4 + A5 = A6

A5

A4

A1 = A2 =A3 = A4 =A5 =A6 =


In a parallel circuit, the potential difference across each bulb is the same as the potential difference across the battery.

V2

V3

V1

Potential difference in parallel circuits

V1 = V2 = V3

V1 =

V2 =

V3 =

Copy the circuit into your books

Measure the voltage at points V1, V2 and V3

Write down your readings:


Summary

Current Voltage

Series Stays the sameSplit up across components

ParallelSplit up between

branchesStays the same

Movie


Comparing circuits


Uses of Circuits

There are two main reasons why parallel circuits are used more commonly than series circuits:

1) Extra appliances (like bulbs) can be added without affecting the output of the others (they are all as bright as each other)

2) If one appliance breaks it won’t affect the others either

An example question:

V1

V2

6V

3A

A1

A2

V3

A3


6V

3V

6V

3A

2A

1A

3V

3A


Resistance 19/04/23Aims:•To understand the affect of increasing resistance•To use Ohm’s law•To interpret a current voltage graph

Starter:


Which Resister is Which?

V

A

1. Setup the circuit2. Use the power pack to

change the voltage3. Make sure you get at least

5 different results.4. Write your results in a

table5. Repeat for the other two

resisters6. Plot your results on a

graph7. V on the X axis8. I on the Y axis9. Calculate the gradient of

your graph (1/gradient = the resistance of the resistors)


I

V


George Simon Ohm 1789-1854

Ohms Law

Resistance is anything that will RESIST a current. It is measured in

Ohms, a unit named after me.

The resistance of a component can be calculated using Ohm’s Law:

Voltage = Current x Resistance

(in V) (in A) (in )

Very = Important x Rabbits

V

RI



V

A

1) What is the resistance across this bulb?

2) Assuming all the bulbs are the same

what is the total resistance in this

circuit?Voltmeter reads 10V

Ammeter reads 2A


Resistance recap

Aims:•To understand the affect of increasing resistance•To use Ohm’s law•To interpret a current voltage graph


Voltage, Current and Resistance 1 19/04/23

Aims:• To use Ohm’s law• To interpret a current voltage graphs of diodes,

bulbs and resistors

Starter: Copy and Complete the Table

Symbol Units Unit Symbol

Charge Q coulomb C

Current I Amps

Resistance R

Voltage

Power

Energy


I

V

Ohmic Resistor:


George Simon Ohm 1789-1854

Ohms Law

Resistance is anything that will RESIST a current. It is measured in

Ohms, a unit named after me.

The resistance of a component can be calculated using Ohm’s Law:

Voltage = Current x Resistance

(in V) (in A) (in )

Very = Important x Rabbits

V

RI



V

A

1) What is the resistance across this bulb?

2) Assuming all the bulbs are the same what is the total resistance in this circuit?Voltmeter

reads 10V

Ammeter reads 2A

WorksheetHomework


Voltage and Current in a Diode

V

A

1. Setup the circuit2. Use the Rheostat to

change the voltage3. Make sure you get at

least 10 different results both positive and negative.

4. Write your results in a table

5. Plot your results on a graph

6. V on the X axis7. I on the Y axis8. Repeat for a bulb

V

A


Investigating current and voltage


Voltage, Current and Resistance 1 recap


bulbs and resistors


Voltage, Current and Resistance 2 19/04/23


bulbs and resistors


Current voltage graphs


nichrome

copper

This means that the copper wire has a lower resistance than the nichrome wire. What does the gradient tell you about resistance?

cu

rren

t (A

)

voltage (V)

Is resistance the same in all wires?

The steeper the gradient of a current-voltage graph, the lower the resistance of the wire.


Current – voltage graphs


Current-voltage graph for a bulb


Current voltage graph for a diode


Current-Voltage Graphs

I

V I

V

I

V

1. Resistor 3. Diode

2. Bulb

Draw and explain the shape of each graph.


Thermistor

A thermistor lets through more current when it is hot because its resistance _______ decreases

Answer in full sentences1. What can you use a

thermistor to sense?2. Name 2 places you will

find one in your homeR

esis

tan

ce /

Temperature / C

xx

xx x

x x

x

x

Use a multimeter, a thermistor and your fingers to answer the question below and then copy it into you book


Light Dependant Resistors (LDR)

When light falls on an LDR it lets through _______ current because its resistance falls.

more

Answer in full sentences1. What can you use a

LDR to sense?2. Where would you find

one outside?R

esis

tan

ce /

k

Light intensity

xx

xx x

x x

x

x

Use a multimeter, a LDR and your fingers to answer the question below and then copy it into you book


Voltage, Current and Resistance 2 recap


bulbs and resistors


Revision 19/04/23Aims:• Revise


Safety device How it works / Notes

Fuse

• Melts when too much current flows.• Value of fuse must be higher than current

drawn by the device• Must be in live wire

Circuit Breaker

• Breaks the circuit when too much current flows• Must be in live wire• Can be reset

Earth

• Protects from shock with metal cased appliances

• Any charge on outside case will be dissipated to earth (also causing the fuse to melt)

Double Insulated

• Plastic exterior means that even if live wire touches case user will not receive a shock

PlasticInsulator

• Grips outer cable and prevents strain on the inner coloured wires.

• Is an insulator, stops current flowing from wire


Earth Wire

Outer Insulation

Cable Grip

Neutral Wire Fuse

Live Wire


Definitions

DefinitionSymbol

UnitUnit Symbol

Voltage Push on the electrons V Volts V

Current Rate of flow of electrons I ampere A

ChargeTotal number of charged particles

Qcoulom

bC

Energy Amount of energy given to a component

E joule J

Resistance

How hard it is for electrons to flow

R ohm Ω

Power How fast energy is transferred P watt W


Equations

Mnemonic Equation Units

Exercise Is Very tiring E = I V t J = A V s

Peter Is a Veggie P = I V W = A V

QuIt Q = I t C = A s

Very Important Rabbits V = I R V = A Ω


IV Graphs 1/gradient = Resistance So steeper the graph lower the resistance

I

V I

V

I

V

1. Resistor 3. Diode

2. Bulb


Circuits

Series Circuit

Parallel Circuit

Current same split

Voltage split same

Series Circuits:•Less Cabling

Parallel Circuits:•Same voltage across all components•If one breaks rest still workCopy down the sketch on the board and annotate it.

PE Teachers = VoltagePupils = electronsRate of pupils moving = CurrentOther Teachers counting Pupils = AmmeterObstacles = Resistances (e.g. Resistors, bulbs, motors ...)Short cuts = Short circuits


ElectricityMains

Definitions

Equations

Circuits

Definition Symbol Unit Unit Symbol


Current Rate of flow of electrons

Charge Total number of charged particles

Energy Amount of energy given to a component

Resistance How hard it is for electrons to flow

Power How fast energy is transferred



Peter is a Veggie

QuIt

Very Important Rabbits

IV Graphs

Resistor Bulb Diode

I

V

Component Function Symbol

Diode Only lets the current through one way

Thermistor Senses _____ (low ______ high _____)

LDR Senses _____ (low ______ high _____)

Series and Parallel Circuits

Advantage Series:

Series Circuit

Parallel Circuit

Current

Voltage

Advantage Parallel:

Hazards:Frayed CablesDamaged PlugsWaterDon’t play with sockets

• Wiring a Plug:Fuse on the live WireGreen/Yellow: EarthBrown: ______Blue: _______

• Safety Features:Double Insulation: Outer case is _____ so it will always be safe to touch.Insulation: _____ outside cable safe to touchEarthing: outside casing connected to _____Circuit Breaker: Trips if too big a ____ flowsFuse: _____ if too big a ____ flows

I

V

I

V


ElectricityMains

Definitions

Equations

Circuits



Peter is a Veggie P = I V W = A V

QuIt Q = I t C = A s

Very Important Rabbits V = I R V = A Ω

IV Graphs

Resistor Bulb Diode

I

V

Component Function Symbol

Diode Only lets the current through one way

Thermistor Senses Temp (low resistance high temp)

LDR Senses Light (low resistance high light)

Series and Parallel Circuits

Less Cabling

Series Circuit

Parallel Circuit

Current same split

Voltage split same

If one breaks rest still work and/or same voltage

Hazards: Frayed Cables Damaged Plugs Water Don’t play with sockets

Wiring a Plug:Fuse on the live WireGreen/Yellow: EarthBrown: liveBlue: neutral

• Safety Features:Double Insulation: Outer case is plastic so it will always be safe to touch.Insulation: plastic outside cable safe to touchEarthing: outside casing connected to earthCircuit Breaker: Trips if too big a current flowsFuse: melts if too big a current flows

Definition Symbol Unit Unit Symbol


Current Rate of flow of electrons I ampere A

Charge Total number of charged particles Q coulomb C

Energy Amount of energy given to a component E joule J

Resistance How hard it is for electrons to flow R ohm Ω

Power How fast energy is transferred P watt W

I

V

I

V


Circuit Symbols

Wire

Connected Wire

Non connecting wire

Cell

Battery

Power supply

Switch

Voltmeter

Ammeter

Motor

Fuse

Buzzer

Diode

Bulb

Resistor

Thermistor

Variable

Resistor


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