Question

# Name the physical quantity related to the following unit: watt.A. ForceB. PowerC. WorkD. Pressure

Hint: In mechanics, One watt is the energy consumed by doing one joule for one second. Also, in electrical terms, it can be defined as the current flow of $1A$ of $1V$. Then, it is either work or power, as the terms force or pressure are not related to electricity.

As force is defined as a push or pull or it is the rate of change of momentum. i.e.$force=\dfrac{dp}{dt}=ma^{2}$ Then, its units are given as, $kgm/s^{2} =N$ which is newton.
Power is defined as the rate of doing work. i.e. $P=\dfrac{W.D}{dt}$ with units,$J/s$

Work is defined as the force which causes a body to move. i.e. $work\;done=force\;\times \;distance$ Then, its units are given as joules. $J$

As pressure is defined as force per unit area, i.e.$pressure=\dfrac{F}{dt}$ then its units is given as $N/m^{2}$

But we know that, in mechanics, One watt , is named after the scientist Watt, is the energy consumed by doing one joule for one second. i.e. $1W=\dfrac{1J}{1s}$. And in electrical terms, it can be defined as the current flow of $1A$of $1V$. i.e. $1W=1A\times 1V$.

Thus clearly, force, work or pressure does not have watt as their unit, as their definition doesn’t match the definition of watt. And, the remaining option is only, power, whose definition matches with the definition of watt, thus the physical quantity, power has the unit watt.
Hence, the correct answer is option B.

Note:
The unit watt,is named after the scientist Watt, who discovered the steam engine. Power is used to measure work in two different contexts, one in terms of mechanical work and other in terms of electrical work.