1. Last lesson Understand that current is the rate of flow of charge
Looking at current in different circuits

2. cell
energy ☺
electron
lamp

3. Coulomb of charge (electrons)
Think of it as a “bag of electrons” (containing electrons!) ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺

4. I’m counting how many electrons go past me every second
Current
I’m counting how many electrons go past me every second ☺ ☺ ☺
The number of electrons flowing past a point in the circuit every second. ☺ ☺ A ☺ ☺ ☺ ☺ ☺ ☺
1 Amp = 1 coulomb per second

5. In a series circuit Current is the same at any point in the circuit

6. In a parallel circuit
The current splits (total current stays the same)
2.5 A
2.5 A
1.25 A
1.25 A

7. Today’s lesson
Understand that Voltage is the amount of energy supplied to the circuit.
Looking at voltage in different circuits

8. Voltage(emf) ☺ V
I’m checking the difference in energy (per coulomb) between the 2 red arrows
1 Volt = 1 Joule per coulomb

9. Voltage (p.d.) ☺
I’m checking the difference in energy (per coulomb) before and after the lamp V
1 Volt = 1 Joule per coulomb

10. Let’s build some circuits to measure voltage☺

11. Stand up! ☺

12. In a series circuit
The sum of the voltages across the lamps equals the voltage across the cells
9 V
3 V
3 V
3 V

13. Can you copy this please?
In a series circuit
The sum of the voltages across the lamps equals the voltage across the cells
9 V ☺
3 V
3 V
3 V
Can you copy this please?

14. In a parallel circuit
In a simple parallel circuit, voltage across each lamp equals the voltage across the cells
5 V
5 V
5 V

15. Can you copy this please?
In a parallel circuit
In a simple parallel circuit, voltage across each lamp equals the voltage across the cells
5 V
5 V ☺
5 V
Can you copy this please?

16. Measuring Voltage (potential difference)
Voltage : measures the amount of energy each electron either receives from the cell or gives to the lamp.
The voltage measured across a cell tells us how much energy each electron is receiving.
The voltage measured across a lamp tells us how much energy each electron is giving to the lamp.

17. Voltmeters
Voltmeters can also be used to measure how much energy is converted by each component.
The voltmeter is connected in parallel to a cell or component (but it is still a series circuit)

18. Homework
Write a letter to a friend who goes to another school but has not started this topic yet.
Explain to him/her how to use a voltmeter. What a voltmeter does and how we use it to measure volts in a series circuit.