Question

Factors affecting the strength of an electromagnet
A. The number of turns in the coil
B. The current flowing in the coil
C. The length if air gap between the poles
D. All

Answer 1

We can start by giving a brief introduction to the electromagnet. Then by taking reference of the formula for magnetic flux density or the magnetic field's strength inside the electromagnet, we have to choose the correct option for this question.

Complete Step-By-Step answer:
We get an electromagnet when we pass current through a conductor. We are aware that when current is passed through a conductor, the magnetic field is being formed around the conductor. The conductor is called an electromagnet because it behaves like a magnet when current is flowing through it. Moreover, an electromagnet's conductor is usually shaped in the form of a compact helical structure similar to the DNA design. Adding on this structure will have multiple numbers of turns and together forming a solenoid.

We know that the equation for magnetic flux density of an electromagnet is,
$\vec{B}=\dfrac{\mu NI}{L}$
Where,
$\vec{B}$= magnetic flux density inside the electromagnet
$\mu$=magnetic susceptibility of the material inside the electromagnet
$N$= number of turns of the electromagnet
$I$= current flowing through the electromagnet
$L$= length of the electromagnet /length of air gaps between the poles

It is important to know that the magnetic flux density represents the strength of the electromagnet.

By looking into the formula, we can say that more the value of $\mu$, greater will the magnetic field. Also, greater the number of turns of the electromagnet, greater the current flowing through the electromagnet, and minimum length of the electromagnet will increase the overall magnetic field.

Hence, option D is the correct answer.

Note:
Electromagnets with good magnetic fields called strong electromagnets are used in our daily appliances such as speakers, microphones, etc. They are designed in such a manner that they give the best performance with minimal current usage and this is done by increasing the number of turns, using material with high value of $\mu$as core of the electromagnet and using a small electromagnet also becomes quintessential.