With the help of an activity, explain the method of inducing electric current in a coil with the help of a magnet. State the rule used to find the direction of electric current thus generated in the coil.
A current through a horizontal power line flows in west to east direction.
(i) What is the direction of magnetic field at a point directly above it and a point directly below it?
(ii) Name the rule used to determine
(a) The direction of force when a current carrying wire is placed in a strong magnetic field.
(b) Magnetic field in a current carrying conductor.

Explanation

A moving magnet induces a current in the coil.
(1) Take a coil wire AB having a large number of turns.
(2) Connect the two ends of the rod to the galvanometer. When a strong magnet is brought towards one of the ends of the rod, the needle in the galvanometer deflects in the left direction indicating the presence of current in the circuit.
(3) When the magnet is moved away from the coil, the needle again rests at zero showing that no current flows in the circuit when the magnet is taken away. (4) The direction of the current can be easily be determined using Fleming.s Right Hand Thumb rule which states that when we stretch the thumb, index finger and middle finger of right hand in mutually perpendicular direction, the thumb points in the direction of motion of conductor, the index finger points in the direction of the magnetic field and the middle finger points in the direction of induced current. (i) The current is in the east-west direction.
Applying the right-hand thumb rule, we get that the direction of magnetic field at a point above the wire is anticlockwise direction. The direction of magnetic field at a point directly above the wire is clockwise direction when viewed from east side. (ii) (a) Using Fleming.s left hand rule (b) Using Right hand thumb rule