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(a) How is the strength of the magnetic field at a point near a straight conductor related to the strength of the electric current flowing in the conductor?

(b) With the help of a diagram describe an activity to show that a straight conductor carrying current produces a magnetic field around it. State the rule which may be used to determine the direction of magnetic field thus produced.

(c) Why do two magnetic field lines never intersect each other? Explain.

Answer:

(a) The magnetic field produced around a straight current carrying conductor increases on increasing the strength of current in the conductor or vice-versa.

(b) Maxwell?s right hand thumb rule indicates the direction of magnetic field for a known direction of current. If the thumb of the right hand points along the direction of current then the curled fingers of that hand gives the direction of the magnetic field due to the current.

When thumb is upwards, the curled fingers are anti-clockwise. So, magnetic field is anti-clockwise.

When thumb is downwards, the curled fingers are clockwise. So, magnetic field is clockwise.

(c) The two magnetic field lines can never intersect each other because if it does so, then two tangents can be drawn at the point of their intersection which will give two directions of the field from the same point, which is impossible.