Question

Which is the S.I unit of electrical power?
A. watts
B. joules
C. volts
D. ampere

Answer 1

Hint: Generally rate of doing work is defined as power. Generally electrical power of electronic instruments given as 10W , 100W etc.
In the above option there is only one option: start with W. That is a unit of electrical power.

Complete step by step answer:
Basically power is known as the energy (work done) supplied by any energy source to the per unit time.
As we know, the rate of doing work is known as power. So electrical power is defined as the rate of doing work in an electric circuit.
Formula for electrical power is
By ohm’s law
$V=IR$
So $P=VI$
By substituting $V=IR$
$P={{I}^{2}}R$
$P=\dfrac{{{I}^{2}}{{R}^{2}}}{R}$
$P=\dfrac{{{V}^{2}}}{R}$
Unit of electrical power is Watt.
Bigger electrical machine use unit of electrical power is kilowatt (KW).
Where $1KW=1000W$
S.I stands for international system. In this unit of electrical power is Watt. We represent it as W.
Also we use different units of power as horsepower (H.P.). whereas 1 Horse power is equal to 746 Watt.
1 H.P.= 746 Watt

Hence, the correct answer is option A.

Note:
The commercial unit of electrical power is kilowatt (KW). We can write $1KW=1000W$
We can also say the unit of electrical power is joule per second.
$1\,watts\,=1\,joule\,per\,\sec ond$