Voltage/Potential Difference
Electricity and Magnetism

Predicting and measuring voltages

Classroom Activity for 11-14 Supporting Physics Teaching

What the Activity is for

Having demonstrated what is involved in measuring voltages, the pupils are now given the opportunity to make some measurements for themselves. The approach taken is to encourage the pupils to think about and talk through the voltage ideas first, before making the actual voltage measurements. To this end, the pupils are asked to make predictions of voltage values before they make each measurement.

What to Prepare

  • batteries, bulbs, voltmeters, connecting leads
  • printed copies of the support sheet: Predicting and measuring voltages (see below)

What Happens During this Activity

You might introduce this activity in the following kind of way:

Teacher: OK, we have the idea that the voltmeter measures how much energy is shifted by the charged particles as they move around the circuit. So, in this first circuit you measure the battery voltage and this gives the number of joules of energy which are shifted by each coulomb of charge. If you then measure the voltage across the bulb what would you expect to get?

Teacher: First of all talk it through with your partner. Think about what we've been saying about energy and voltage.

Teacher: OK, people are suggesting that the voltage should be the same in both places. As Anita says the energy put in at the battery comes out at the bulb.

Teacher: Well, collect the equipment and use a voltmeter to measure the voltage values for yourselves. There are three circuits to investigate. Go to it!

For this activity, the pupils should ideally work in pairs. Each pair should have one voltmeter, which is placed in the different positions in the circuits as shown on the support sheet.

As the pairs of pupils complete their measurements, it is a good idea to collect the voltage values on the board or on a large sheet of poster paper, so that the pattern of findings becomes apparent to all.

Be sure to give the pupils an opportunity to talk through these new ideas during the lesson as they review the voltage values for the whole class.

Resources

Download the support sheet / student worksheet for this activity.

Voltage/Potential Difference
can be measured using Voltmeter

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