Kettle Power

Two electric kettles of different power ratings (e.g., 1 kW and 3 kW) are compared to show how electrical power relates to the rate of energy transfer. The demonstration illustrates that the higher-power kettle boils water faster and reinforces the relationship P = IV.

1. Plug each kettle into a separate power meter and wall socket (do not use extension leads).
2. Set both meters to measure voltage and record the readings.
3. Pour the same volume of water (e.g., 0.5 liters) into each kettle, measuring initial water temperature if desired.
4. Switch on both kettles simultaneously.
5. Change the meters to measure current and note the values.
6. Switch meters to power mode to display electrical power.
7. Observe which kettle boils first and discuss the relationship between voltage, current, and power.

📄 Kettle power - Institute of Physics: https://spark.iop.org/kettle-power

• Try using different volumes of water to compare boiling times.
• Test kettles of other power ratings (e.g., 2 kW) to expand the comparison.
• Use a thermometer to track temperature increase over time and compare heating rates.

• Plug kettles directly into wall outlets, not extension leads, as high-power kettles draw large currents.
• Ensure kettles are on stable surfaces to avoid spills and burns.
• Handle hot water carefully to prevent scalding.
• Check that the lab’s electrical circuits can handle both kettles running simultaneously.

• Which kettle boils the water first? (The higher-power kettle boils water faster.)
• Why does the larger kettle draw a higher current? (It has lower resistance, so for the same voltage it allows more current.)
• How does power relate to current and voltage? (P = IV, so power increases with higher current at the same voltage.)
• Why does the smaller kettle not boil faster even though it looks more compact? (Both kettles contain the same mass of water, so the energy needed is the same; only the power rating changes the rate of heating.)