Voltage Value

Ask the children to make a circuit following the drawing on the worksheet and to check that it works. They should notice the type of battery and bulb in the circuit. You could point out that a 1.5V ‘battery’ is really a cell and that ‘battery’ means a series of cells used together: for example, a 3V battery contains two 1.5V cells and a 4.5V battery contains three cells.

Ask them to discuss and then predict what difference will be made if the bulb is exchanged for a 2.5V, 3.5V or 6V bulb. They might predict that the higher voltage bulbs will be brighter. Before they measure the brightness of the bulbs using sheets of thin paper, as explained on the worksheet, ask them what they should do to ensure that the test is fair. A fair test would use sheets of paper of the same type to test each bulb, placed the same distance away from the bulb every time.

The children could record their predictions. Ask if the tests they did supported these or contradicted them. Can they explain why?