Question

Which of the following changes will result in a stronger electromagnet?

A. Using a longer nail

B. Using a lower voltage

C. Using more coils of wire

D. Using a shorter wire

Answer 1

the answer is going to be C

Answer 2

The correct option is C. i.e. Using more coils of wire

Explanation: 

The strength of an electromagnet can be increased in the following ways:

1. By increasing the number of coils.
2. By increasing the current/voltage
3. Using an iron core, increases the strength of the electromagnet.