Question

What current is taken by a $3\,KW$ electrical generator working on $240\,V$ mains?

Answer 1

Hint:In order to solve this question we need to understand electric current and how it flows. Electric current is defined as the number of charges crossing per unit surface area in unit second of time. So a wire is subjected to potential difference then an electric field setup in wire which binds the electrons to move in opposite direction as of applied electric field and hence current flows in direction of applied electric field or in direction of decreasing potential. However when current flows in a wire then wire opposes this behavior and generates opposition known as resistance due to which some of energy is lost in heat.

Complete step by step answer:
According to the problem, the power of an electrical generator is $P = 3\,KW$ or $P = 3 \times {10^3}W$.
And, the voltage used in the electric generator is, $V = 240\,V$.
Let the current taken by the electric generator be $i$ Ampere.
Then by formula of power we get, $P = Vi$.
So the electric current is given by,
$i = \dfrac{P}{V}$
Putting values we get,
$i = \dfrac{{3 \times {{10}^3}W}}{{240Volt}}$
$\therefore i = 12.5A$

So the electric current is, $12.5\,A$.

Note:It should be remembered that electric generator and electric motor, both work on principle of electromagnetic induction law by Faraday’s. Faraday’s law states that whenever there is change in magnetic flux through any loop then the current would be induced in that loop and direction of which is determined from Lenz’s law. According to Lenz’s law, direction of induced current is such that it opposes the cause of its generation, and this law is in accordance with Newton’s first law for motion.