5.1.5—Power as work done per unit time
- Syllabus
- 9702–2028–2029
- Objective
- 5.1.5
- Level
- AS
Power measures the rate at which work is done or energy is transferred
Power is the rate of energy transfer: P=W/t=∆E/t, measured in watts, where 1 W=1 J s⁻¹.
Use the energy transferred over the relevant time interval; average power need not equal instantaneous power when the rate changes.
A device transferring 900 J in 30 s has average power 30 W.
Power is not the same as total work: two machines can do the same work in different times and therefore have different powers.
ConceptA-Level CAIE Physics AS