Question

1. Copy the adjacent diagram and plot magnetic fields around A and B for the circular coil, when the current flows through it.
2. State one way of increasing the magnetic intensity of the circular coil.
3. Give two characteristics of the magnetic field produced by the coil.
4. What is the direction of magnetic field with respect to the plane of circular coil?
5. What polarity (magnetic) is produced on the coil facing you?

Answer 1

(a)

The magnetic field lines are concentric circles around A (anticlockwise) and B (clockwise); near the centre they are almost straight, parallel and perpendicular to the plane of the coil.

(b) The magnetic intensity of the coil can be increased by increasing the number of turns in the coil. Increasing the current or decreasing the radius of the coil also increases it.

(c) Two characteristics of the magnetic field produced by the coil:

1. Near the wire of the coil, the magnetic field lines are concentric circles.
2. Near the centre of the coil, the field lines are almost straight and parallel to each other. This means the field is nearly uniform there.

(d) At the centre, the magnetic field is perpendicular to the plane of the circular coil.

(e) Seen from the front, the current goes up on the left at A, across the top, and down on the right at B. So it flows in the clockwise direction. By the clock rule, the face of the coil towards you becomes a South pole.