How would the strength of magnetic field due to a current-carrying loop be affected, if:
(a) the radius of the loop is reduced to half of its original value, and
(b) the strength of the current through the loop is doubled ? Give reason for your answer.

Explanation

(a) If the radius of current loop is reduced to half of its original value, the strength of magnetic field is doubled as magnetic field. (B) is inversely proportional to the radius (r) of loop.
(b) As strength of magnetic field is proportional to current (1) flowing through the loop `(B prop l)`, the magnetic field is doubled if current is doubled.