ZIMSEC O Level Combined Science Notes: Experiment: Current and Voltage

Aim: To show how current changes with voltage and to find the resistance of a resistor

Materials: Three/Four 1.5V battery cells, ammeter, lamp,resistor, switch, leads with crocodile clips

Method Current and Voltage

1. Set up the series using one cell as shown in the diagram above
2. Measure the current flowing on the ammeter when the switch is closed
3. Place another cell in the series with the first one
4. Measure the amount of the current flowing through the circuit
5. Repeat these steps with 3 and then 4 cells measuring the current each time
6. Put the results in a table and calculate resistance
7. Repeat the experiment using a lamp instead of the resistor
8. Use the data to plot a graph of voltage against current
9. The gradient of this graph is the resistance
10. The formula for finding gradient is:
11. $Gradient = \dfrac{\text{Vertical height(V)}}{\text{Horizontal Distance(I)}}$

Results and Observation

• When the voltage increases the current passing through a circuit also increases
• Current varies directly in proportion with voltage
• Resistance does not change when the voltage increases

To access more topics go to the Combined Science Notes page.