Question

What is the magnetomotive force (mmf) of a wire with $$8$$ turns carrying three amperes of current?
A. $$2400\text{At}$$
B. $$240\text{At}$$
C. $$24\text{At}$$
D. $$2.4\text{At}$$

Answer 1

Hint: First of all, we will obtain the expression which gives the magnetomotive force. It is given by the amount of current flowing through the wire time the number of turns. We will substitute the required values and manipulate accordingly to obtain the answer.

Formula used:
The formula which gives the magnetomotive force is shown below:
$$F_{\text{m}}=N\times i$$ …… (1)
Where,
$$F_{\text{m}}$$ indicates the magnetomotive force.
$$N$$ indicates the number of turns.
$$i$$ indicates the current flowing through the wire.

Complete step by step answer:
In the given question, we are supplied with the following information:
There is a wire, which has eight turns in it.The amount of current flowing through the wire is three amperes.We are required to find the magnetomotive force of the wire.

To begin with, we know that magnetomotive force is the mmf is equal to a number of turns of wire carrying an electric current and has units of ampere-turns.Let us proceed to solve the problem.The magnetomotive force associated with the wire is calculated as:
We substitute the required values in the equation (1) and we get:
$$\begin{gathered} F_{\text{m}}=N\times i \\ \Rightarrow F_{\text{m}}=8\times 3\text{At} \\ \therefore F_{\text{m}}=24\text{At} \end{gathered}$$
Hence, the magnetomotive force is found to be $$24\text{At}$$ .

The correct option is C.

Additional information:
The property of certain substances or phenomena that give rise to magnetic fields is the magnetomotive force, also known as magnetic potential. The magnetomotive force in electricity is similar to the electromotive force or voltage. The ampere-turn is the standard unit of magnetomotive force.

Note: It is important to remember that magnetomotive force (mmf) drives magnetic flux through magnetic circuits, close to how electromotive force (emf) drives a current of electrical charge in electrical circuits. However, the term ‘magnetomotive force’ is a misleading term since it is neither a force nor something moving.