Question

An insulated copper wire is wound on a soft iron core. Current is passed through the coil such that at end ‘A’ the current flows anti- clockwise and a magnetic compass needle placed at other end ‘B’ of the coil.

i) If soft iron core is replaced by a cardboard tube, what will be the effect on the magnetic needle?

ii) What happens to the magnetic needle if the current is stopped?

• A. i) The amount of deflection will increase ii) The needle will return to its original position
• B. i) The amount of deflection will decrease ii) The needle will remain deflected
• C. i) The amount of deflection will decrease ii) The needle will return to its original position
• D. i) The amount of deflection will increase ii) The needle will not be affected
• E. i) The amount of deflection will decrease ii) The needle will deflect in the opposite direction

Answer 1

The correct option is C

i) The amount of deflection will decrease ii) The needle will return to its original position

The extent of deflection will decrease as the magnetic field strength decreases.

The needle will return to its original position (along N-S of the earth) as the coil will get demagnetised.