Electrical energy and electrical power Flashcards – Cambridge IGCSE (9–1) Physics 0972 (Extended) (2026–2028)

What roles do the source and components play in energy transfer in an electric circuit?

The source supplies energy to the components, which transfer it to the surroundings rather than creating it.

What are three ways circuit components can transfer energy to the surroundings?

Heating, producing light, and motion.

What is electrical power?

The rate at which electrical energy is transferred.

What equation relates a component’s power to the current through it and the potential difference across it?

$P = IV$

What are the units of electrical power, current and potential difference?

Power: watts (W); current: amperes (A); potential difference: volts (V).

What is a kilowatt-hour?

The energy transferred when a power of one kilowatt is maintained for one hour.

How many joules are in one kilowatt-hour?

$3.6 \times 10^6\ \text{J}$

How is energy use in kilowatt-hours calculated from power and time?

$E = Pt$ Use power in kilowatts and time in hours. Convert power from watts to kilowatts first if needed.

How is the cost of an appliance’s electricity use calculated?

Multiply the energy used in kilowatt-hours by the price per kilowatt-hour.