### 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**

- Set up the series using one cell as shown in the diagram above
- Measure the current flowing on the ammeter when the switch is closed
- Place another cell in the series with the first one
- Measure the amount of the current flowing through the circuit
- Repeat these steps with 3 and then 4 cells measuring the current each time
- Put the results in a table and calculate resistance
- Repeat the experiment using a lamp instead of the resistor
- Use the data to plot a graph of voltage against current
- The gradient of this graph is the resistance
- The formula for finding gradient is:
- 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.