(a) Write three distinguishing features between an alternating current and a direct current. (b) A current through a horizontal power line flows in east to west direction. What is the direction of magnetic field at a point directly below it and at a point directly above it? Name the rule you have applied in this case.

(a) Distinguishing features between an alternating current and a direct current:
Direct Current (D.C.):-
1. Direct current always flows in one direction only.
2. The magnitude of current may or may not remain constant.
3. Current obtained from a battery and D.C. generator is D.C.
Alternating Current (A.C.)
1. Alternating current reverses its direction periodically.
2. Magnitude of current continuously changes with time.
3. Current obtained from an A.C. generator and current in our domestic circuit are A.C