Question

The diagrams (a), (b) and (c) show a smooth, but stiff cardboard, held horizontally, such that a thick copper wire passes through the middle of cardboard. The direction of the current is shown by arrows. Copy the diagrams.

1. In the diagrams (a) and (b) show the magnetic field due to conductor, showing at least four magnetic lines force. Assume there is no magnetic field due to earth.
2. In the diagram (c) show the magnetic field due to conductor when earth's magnetic field is acting by four magnetic lines of force.

Answer 1

(a) Magnetic lines of force are concentric circles around the conductor, in the anticlockwise direction (seen from above).

(b) Magnetic lines of force are concentric circles around the conductor, in the clockwise direction (seen from above).

(c) Near the conductor the lines are circular, and away from it they are almost straight and point north due to the earth’s field. A neutral point (X) is formed on the west side of the conductor, where the field of the conductor is equal and opposite to the earth’s field.