Chapter Work

• Power is defined as the rate of doing work or the rate of transfer of energy.
• If an agent does a work $W$ in time $t$, then power is given by: $$Power = \frac{work}{time}$$

$$or$$

$$P = \frac{W}{t}$$

• The unit of power is $watt$, symbolized by $W$, named after James Watt (1736-1819).
• 1 watt is the power of an agent that does work at the rate of 1 joule per second.
• Thus, power is $1W$ when the rate of consumption of energy is $1Js^{-1}$.
• We express larger rates of energy transfer in kilowatts ($kW$).

$$1 kilowatt (kW) = 1000watts (W)$$

$$1 kW = 1000 W = 1000 Js^{-1}$$

• The power of an agent may vary with time, meaning it may do work at different rates at different intervals.
• Therefore, the concept of average power is useful, obtained by dividing the total energy consumed by the total time taken.

Rate of doing work