Voltage - an activity

What the Activity is for

First of all, attention is focused on introducing what is meant by voltage. It is important that pupils have an understanding of what it is that they are measuring when they measure voltages in different parts of a circuit.

What to Prepare

• 12 volt direct current power supply
• 12 volt, 24 watt bulb in holder
• connecting leads

What Happens During this Activity

It is a good idea to start with a demonstration of what happens in a simple circuit when the voltage of the supply is changed. You might start with the output of the power supply at about 6 volt and then switch it up to about 12 volt. You might also make links here to the practical work carried out by the pupils earlier in which they changed the number of batteries in a circuit.

Teacher: OK, so we start with the power supply set down here at around 6 volt. What do you notice about the brightness of the bulb?

Bill: It's dim.

Teacher: Yes, that's right. Now supposing I turn up the power supply here, increase the voltage on this scale. What do you think will happen? Predictions?

Jill: It'll get brighter.

Teacher: Well, let's give it a go [teacher turns up voltage]. Brighter yes. Where have you seen this kind of thing before?

Jill: If you add batteries it makes the bulb brighter.

Teacher: That's right! So if I add batteries or turn up the voltage, what happens with the bulb?

Bill: You get more energy from the bulb.

Teacher: Excellent! In fact the voltage is a measure of how much energy is provided by the battery for the charged particles in the circuit. If I increase the battery voltage more energy is shifted by the bulb. The bulb gets brighter.