Which electromagnet would have the most strength?
a) an electromagnet with 5 coils.
b) an electromagnet with 10 coils.
c) an electromagnet with 15 coils.
d) an electromagnet with 20 coils.

D) An electromagnet with 20 coils.

Explanation:

An electromagnet will produce magnetic field on its axis given by the equation

here we know that

= number of turns per unit length

i = current in the coil

Now if we need to increase the magnetic field strength of the electromagnet then we can increase its turns

so we will have

D) An electromagnet with 20 coils.

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