A coil is wrapped around the full length of a tube through which a soft iron rod is inserted. An aluminium ring is placed over the upper end of the rod. The time for the ring to fall is noted. When an alternating current is passed through the coil the time of fall is seemed to increase slightly.

I have to design a lab experiment to investigate how some variable factors or measurable details would affect the time of fall. What are the variable factors???? Can u help plz. Thx

Some of the variables to consider would be the type of material the coil is made of, the thickness of the wire, and the strength of the current. Hope that helps!