A metallic weight is suspended from a metal spring If now a

A metallic weight is suspended from a metal spring. If now a current is passed through the spring, the spring will contract raising the weight. the weight will not move. whether or not the weight moves up or down depends on what the weight is made of (i.e. whether or not it is magnetizable). the spring will extend, lowering the weight. None of these are true. A 5 H inductor carries a current of 2 amps. How can a self-induced EMF of 50 volts be made to appear across the inductor? Change the current at the rate of 10 amps/sec. Change the current uniformly to zero in 20 seconds. Change the current to 10 amps. Break the circuit instantaneously. None of these.

Solution

1)
A) The spring will contract , raising the weight

   current in each close by ring is in same direction so wires attract each other
2) Change the current at the rate of 10 amps/sec

V= Lx dI/dt   
50 = 5x10