Energy & Power in Circuits

Aim: To investigate what determines how much energy a component transfers.

Part A — Does the time matter?

1. Select the Heater and set the supply to 12 V. Read the voltmeter and the ammeter carefully.
2. Start the timer, let it run for about 30 seconds, then stop it. Record the component, voltage, current and time in the table.
3. Reset the timer and repeat, this time letting it run for about twice as long.
4. Calculate the energy transferred for both runs and add your answers to the table. When the time roughly doubled, what happened to the energy transferred?

Part B — What does the supply voltage change?

1. Keep the Heater selected. Set the supply to 6 V, read the meters, and time a 30-second run. Record everything in the table.
2. Repeat at 9 V and at 12 V, timing about 30 seconds each time.
3. Calculate the power for each run. Look down your table: as the voltage goes up, what happens to the current — and what happens to the power?

Part C — Comparing the three components

1. Set the supply to 12 V. For the heater, then the lamp, then the motor, read the voltmeter and ammeter and time a 60-second run for each.
2. Calculate each component's power, and the energy each one transfers in its 60 seconds. Add your answers to the table.
3. Rank the three components by power, then by energy transferred. Using your table, explain how a component's energy transfer is connected to its power and to the time it runs for.

Part D — A closer look at the lamp

1. Select the Lamp and record the voltage and current at 3 V, 6 V and 12 V (no timing needed for this part).
2. Each time the voltage doubles, does the lamp's current double too? Take the same readings for the heater and compare.
3. Look at how the lamp glows brighter as the voltage rises. Suggest what might be happening inside the filament that makes the lamp behave differently from the heater.