Task : Copy and fill in the blanks

Electrons are ………….. charged sub-atomic particles. They move around the circuit through

……………. materials such as metal wires. A cell has a positive and negative side. The ………..

flow out of the negative side and ……….. the positive side. This is called the electron flow.

electrons negatively towards conductive

Modelling Electricity To be able to use a model to explain current and voltage in

electrical circuits

Symbols Look at the following symbols for components – can you name them all?

Cell Resistor Bulb Switch

Battery Buzzer Fuse Voltmeter

Ammeter Motor Variable Resistor

Key Terms What is current, voltage and resistance?

Current – the flow of electrons around the circuitVoltage – driving force which pushes the current aroundResistance – anything in the circuit which slows the flow

down

Task 2: Voltage and current = the electrical energy

Voltage is a measure of the energy carried

voltage Current

Voltage is used up in components

Voltage is measured in volts, V

Voltage is measured with a voltmeter

Current is the rate of flow

Current is not used up, what flows into a component

must flow out.

Current is measured in amps (amperes), A

Current is measured with an ammeter

Series Circuits What are series circuits?

Series circuits are ‘all or nothing’ – the different components are connected in a line, end to end

Disconnecting one component breaks the circuit, meaning all the components stop

+ -A

The same current flows through all parts of the circuit

The size of the current depends on the voltage and resistance (I = V/R)

The total voltage is shared between the components - the bigger the resistance of a component the bigger its share of the voltage

Series Circuits

+ -A

6V

2V

2.5V

1.5V

0.5A

Voltages add to equal the supply: 1.5V + 2V + 2.5V = 6V Total resistance is the resistance of all the components: 3Ω +

4Ω + 5Ω = 12Ω

Current = voltage ÷ resistance: 6 ÷ 12 = 0.5A

5Ω3Ω

4Ω

Parallel Circuits What are parallel circuits?

In parallel circuits each component is separately connected to the +ve and –ve of the supply

Removing one component barely affects the others

All components get the full voltage The current through each component

depends on its resistance – the lower the resistance the more current that flows through

The total current flowing around the circuit is equal to the total of all the currents in the separate branches

branch 1

branch 2

Parallel Circuits

+ -6V

5.5A

Voltages are all equal to the supply: 6V Total resistance is less than the smallest resistance: <2Ω

Current (A1) equals the sum of all the branches: A2 + A3 + A4 etc… (5.5A)

4Ω

A1

A2

A3

A4

6V

6V

6V

1.5A

3A

1A

2Ω

6Ω

Assessment Complete the circuits

worksheet

Assessment1. E, F, T, J, or L

2. A, B, C, D, G, H, or K

3. A and I

4. Add some more cells (>2 cells = a battery)

5. B

6. B, D, G, H, or K (2 of these)

7. A or C

8. The switch is open

9. B, D or K

10. F

Assessment11.

V

V

12. B, D or K

Assessment13.

14. 6A – the current should split evenly down each branch if the resistance of the components in each branch is equal

15. 2.5V – the voltage is shared between all the components in a series circuit