1. Current-Potential Difference Graphs
Aim: To explain the graph shapes which
show how current changes as voltage
changes in electrical components.

2. Starter
Draw a circuit diagram showing a battery of two cells and a resistor.
Add an ammeter and a voltmeter to measure current and voltage across the resistor.

3. Starter A V

4. Current-Potential Difference Graphs
We can plot a current-potential difference graph for an electrical component if we measure them and draw a graph.
Voltage, or potential difference, is the independent variable – we change this by altering the number of cells in a battery.
Current is the dependent variable – we measure the effect that voltage has on it.

5. Current-Potential Difference Graphs
Prediction
Make a prediction – how do you think the current will change as the voltage changes?
Why do you think this?

6. Current-Potential Difference Model
1.5V
0.22A
Decrease voltage
Increase voltage
1.4V

7. Current-Potential Difference Model
1.5V
1.5V
0.44A
Decrease voltage
Increase voltage
2.7V

8. Current-Potential Difference Model
1.5V
1.5V
1.5V
0.68A
Decrease voltage
Increase voltage
4.3V

9. Current-Potential Difference Model
1.5V
1.5V
1.5V
1.5V
0.94A
Decrease voltage
Increase voltage
5.9V

10. Current-Potential Difference Model
1.5V
1.5V
1.5V
1.5V
1.5V
1.16A
Decrease voltage
Increase voltage
7.3V

11. Current-Potential Difference Graph - Resistor
Draw a graph to show the results.
Current
Voltage

12. What if you turn the battery round?
1.5V
-0.22A
-1.4V

13. What if you turn the battery round?
Current
Voltage

14. Why is the graph this shape?
As the voltage increases the current increases proportionally.
This is because the electrons are moving faster because they are being given more energy.
When you turn the battery round the electrons move in the opposite direction.

15. Why is the graph this shape?
1.5 V e e e e e e e e e e e
Decrease voltage
Increase voltage

16. Why is the graph this shape?
3 V e e e e e e e e e e e
Decrease voltage
Increase voltage

17. Why is the graph this shape?
4.5 V e e e e e e e e e e e
Decrease voltage
Increase voltage

18. Current-Potential Difference Model
1.5V
0.30A
Decrease voltage
Increase voltage
1.4V

19. Current-Potential Difference Model
1.5V
1.5V
0.55A
Decrease voltage
Increase voltage
2.7V

20. Current-Potential Difference Model
1.5V
1.5V
1.5V
0.90A
Decrease voltage
Increase voltage
4.3V

21. Current-Potential Difference Model
1.5V
1.5V
1.5V
1.5V
1.05A
Decrease voltage
Increase voltage
5.9V

22. Current-Potential Difference Model
1.5V
1.5V
1.5V
1.5V
1.5V
1.10A
Decrease voltage
Increase voltage
7.3V

23. Current-Potential Difference Graph - Filament lamp
Draw a graph to show the results.
Current
Voltage

24. What if you turn the battery round?
Current
Voltage

25. Why is the graph this shape?
As the voltage increases the current increases.
BUT the current increase gets smaller as the voltage gets larger. Why?
This is because the filament is heating up. The particles in the filament are vibrating more, meaning they get in the way of the electrons flowing through.
This slows the electrons down – resistance.

26. Why is the graph this shape?

27. Why is the graph this shape?

28. Current-Potential Difference Graph - Diode
Sketch the graph for these results
Voltage (V)
Current (A)
7.9
97.5
6.4
76.7
4.9
55.9
2.4
21.3
1.4
7.3
0.9
5.5
0.1
0.0
-1.9
-6.4
-8.9

29. Current-Potential Difference Graph - Filament lamp
Draw a graph to show the results.
Current
Voltage

30. Why is the graph this shape?
As the voltage increases the current increases.
There are no negative values because current can only flow one way in a diode.
The line is very steep because current can flow very quickly in the correct direction.

31. Knowledge Check What happens to current as you increase voltage?
A It stays the same
B It increases
C It decreases
Why?
– The electrons are being
given more energy

32. Knowledge Check Which is the correct current-potential difference
graph for a resistor?
Voltage
Current
Current
Voltage
Current
Voltage
Why?
A B C
- Current increases proportionally to potential difference

33. Knowledge Check Which is the correct current-potential difference
graph for a filament lamp?
Current
Current
Current
Voltage
Voltage
Voltage
A B C
Why?
- Current doesn’t increase as fast when the lamp gets warm at a high voltage.

34. Knowledge Check Why does resistance increase in a filament lamp
as you increase the voltage?
A Electrons move slower when voltage increases.
B Electrons move slower at high temperatures.
C Particles in the wire vibrating bump into the
electrons and slow them down.

35. Knowledge Check Which is the correct current-potential difference
graph for a diode?
Current
Voltage
Current
Current
Voltage
Voltage
A B C
Why?
- Current only flows in one direction. It flows very fast in this direction.