CBSE Class 10 Answered

 Power (symbol: P) is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time. As a rate of change of work done or the energy of a subsystem, power is:

where P is power, W is work and t is time.

The average power (often simply called "power" when the context makes it clear) is the average amount of work done or energy transferred per unit time. The instantaneous power is then the limiting value of the average power as the time interval Δt approaches zero.

When the rate of energy transfer or work is constant, all of this can be simplified to

,

where W and E are, respectively, the work done or energy transferred in time t (usually measured in seconds).