Question

What is the magneto motive force in a 75-turn coil of wire when there are 4A of current through it?
A. 18.75 At
B. 30 At
C. 300 At
D. 187 At

Answer 1

Hint: We are given the number of turns and current of a coil of wire and are asked to find the magneto motive force through the wire. We have an equation to find the magnetomotive force through a wire. By substituting the given values in the equation we will get the required solution.

Formula used:
$F=NI$

Complete step-by-step answer:
In the question we are given the number of turns and current passing through a coil.
Let ‘$I$’ be the current passing through the coil. Then from the question we have the current as,
\[I=4A\]
Let ‘N’ be the total number of turns of the coil. Then we are given,
$N=75$
We are asked to find the magneto motive force in the coil.
We know that the equation for magneto motive force is given as,
$F=NI$, where ‘F’ is the magneto motive force, ‘N’ is the total number of turns of the coil and ‘$I$’ is the current passing through the coil.
Since we know the values of the total number of turns and the current passing through the coil, we can substitute them in the above equation.
Thus we get,
$F=75\times 4$
$\Rightarrow F=300At$
Therefore we get the magneto motive force in the coil as 300 At.

So, the correct answer is “Option C”.

Note: Magnetomotive force is an analogue of electromotive force. It is also known as the magnetic potential and it drives the magnetic flux through the magnetic circuits. It is calculated as the number of turns of coil of wire carrying a current through it. And the unit of magnetomotive force is ampere – turns (At).