Question

 Unit of electric power may also be expressed as:
A. Volt ampere
B. Kilowatt hour
C. Watt second
D. Joule second

Answer 1

Hint: The unit of electric power can be found by using the units of work and time, as electric power is the work done or energy given per unit time. Mathematically,
\[P=\dfrac{W}{t}\] , where P is electric power, W is the work done and t is time.
So, to obtain units of electric power we will divide units of work and time. After obtaining the unit of power we can compare it with units of the given option.

Complete step by step answer:
 The S.I. base units are also known as fundamental units. These include kilogram, second, Ampere, meter, Kelvin, Mole and candela. S.I. units of all other physical quantities are derived from them.
Electric power is the rate of work done by the electrostatic force. Mathematically we can write
\[P=\dfrac{W}{t}\]
The unit of work is Joule and is represented by J.
The unit of time is seconds and is represented by s.
So, unit of electric power will be
Joule/seconds or J/s
The S.I unit of power is Watt. It is represented by W
$W=\dfrac{J}{s}$
Let us check the options,
The first option is Volt Ampere, volt can be written as joule per coulomb and ampere can be written as coulomb per seconds. So we have
$V\times A=\dfrac{J}{C}\times \dfrac{C}{s}=\dfrac{J}{s}$,
This is a unit of power.
 In both the options B and C, the unit given to us is a product of unit of power and unit of time. So both options are incorrect.
In option D we are given the unit joule second but we know that unit of power is joule per second. So option D is also incorrect.
Hence the correct option is A.
Note: Electric power is a derived quantity, so its unit is made from the base S.I. units. The unit of electric power can also be given as a product of volt and ampere i.e. volt ampere. Dimension of electric power is
$ML{{T}^{-3}}$