Question

Make four electromagnets with 20, 40, 60, and 80 turns. Connect them one by one to a battery of 2 cells. Bring the electromagnet near a box of pins. Count the number of pins attracted by it. Compare the strengths of the electromagnets.

Answer 1

Students count the pins themselves. If we compare the strength of different electromagnets having 20, 40, 60, and 80 turns the electromagnet having 80 turns has the largest strength. 

This activity shows that:

Strength of magnet ∝ Number of turns