Question

Three plotting compasses are to a solenoid carrying a current. How many of the compass needles will change direction, if the current through the solenoid is increased? 

(Ignore the effect of the earth’s magnetic field). 

A. Only I compass needle 

B. 2 compass needle 

C. 3 compass needle 

D. None of the above

Answer 1

Since the magnetic field outside the solenoid is zero because it gets cancelled due to the each circular ring. Hence no compasses will get deflected.