Question

1. The diagram alongside shows a freely suspended copper conductor carrying current held in between the pole pieces of a permanent magnet. State whether conductor will move into the plane of paper or out of the plane of paper.
2. Why does copper conductor move?
3. State the rule which determines motion of conductor.
4. State three factors which determine the force acting on conductor.

Answer 1

(a) The conductor will move into the plane of paper. Applying Fleming’s left-hand rule to the directions shown in the diagram, the thumb points into the plane of paper, so the force on the conductor is directed into the plane of paper.

(b) The copper conductor moves because a current-carrying conductor placed in a magnetic field experiences a force. This force arises due to the interaction between the magnetic field produced by the current in the conductor and the external magnetic field of the permanent magnet. This is called the magnetic Lorentz force.

(c) Fleming’s left-hand rule determines the direction of motion of the conductor. Stretch the thumb, forefinger and middle finger of the left hand mutually at right angles to each other, such that the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current. Then the thumb gives the direction of motion of the conductor.

(d) The force acting on the conductor depends on:

1. The strength of the current flowing through the conductor, I.
2. The intensity of the magnetic field, B.
3. The length of the conductor lying inside the magnetic field, l.

Thus, F = BIl.