1. ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺ ☺

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 coulombs of electrons go past me every second
Current
I’m counting how many coulombs of electrons go past me every second ☺ ☺ ☺
The rate of flow of electric charge (number of Coulombs flowing past a point in the circuit every second).
I = ΔQ/Δt ☺ ☺ 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. Voltage(emf) ☺ V
I’m checking the difference in energy (per coulomb) between the 2 red arrows
1 Volt = 1 Joule per coulomb

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

9. In a series circuit
The sum of the p.d.s across the lamps equals the emf across the cells
9 V
3 V
3 V
3 V

10. In a parallel circuit
In a simple parallel circuit, p.d. across each lamp equals the e.m.f. across the cells
5 V
5 V
5 V

11. Resistance
Measures how difficult it is for current to flow. Measured in Ohms (Ω) A V
Resistance = voltage/current R = V/I

12. Ohm’s Law
V = IR V R I X

13. Adding resistances

14. In series?

15. Adding resistors in series

16. Examples

17. Adding resistors in parallel

18. Adding resistors in parallel

19. Examples

20. Other examples

21. Resistance R is proportional to the length of wire – WHY? R α L
R is inversely proportional to the cross sectional area of wire – WHY?
R α 1/A
R depends on the type of material – WHY?

22. Resistivity R = ρL A where R = resistance in Ohms
L = Length of conductor in metres
A = cross sectional area of conductor in m2
ρ = resistivity of the material in Ohms.meters