Name: Earth's Magnetic Poles
Uploaded: 2019-07-19
Duration: 3 min 53 s
Description: Let us explore the concept of true north and the magnetic north pole of the Earth and try to locate the poles using the concepts behind them in this video.

Question

Explain magnetic lines of force and write properties. Draw diagram.

Accepted Answer

A magnetic field, like an electric field, can be represented by lines, called ‘magnetic lines of force’. When a compass needle is placed in the magnetic field of a bar-magnet, the needle rests in a definite direction. As the needle is moved in the field, its direction goes on changing continuously. The path of the compass-needle is a curved line which originates from the north pole of the magnet and terminates at the south pole. This is a line of force. Thus, the lines of force in a magnetic field are those imaginary lines which continuously represent the direction of the magnetic field. The tangent drawn at any point on a line of force shows the direction of magnetic field at that point. Fig. show the magnetic lines of force of the field due to a current-carrying solenoid and a tar-magnet respectively. The similarity of lines again shows that a solenoid and a bar-magnet are identical in magnetic behaviour.

Properties : (i) The magnetic lines of force emerge from the north pole and, following a curved path, enter the south pole and reach back the north-pole moving inside the magnet. Thus, these are closed loops through the magnet. (Electric lines of force are not closed loops.)
(ii) Two lines of force never intersect each other. If they ever did so, there would have been two tangents at the point of intersection, that is, two directions of magnetic field at one point, which is impossible.
(iii) Near the magnetic poles, where the field is stronger, the lines of force are closer. Going away from the poles, the field becomes weaker and the lines become rarer. Thus, larger the number of lines of force at a given point, stronger is the magnetic field at that point.
(iv) In a ‘uniform’ magnetic field, as earth’s magnetic field at a place, the lines of force are parallel and equidistant.

(v) No lines of force will pass through neutral point.
(vi) Magnetic lines of force may enter or come out from a magnetic pole at any angle.
(vii) Between opposite poles (N-S) lines of force may have tendency to attract like a stretched string to contract and between similar poles (N-N) or (S-S) may have tendency to repel

Explain magnetic lines of force and write properties. Draw diagram.

Important Questions on Magnetic Field and Earth's Magnetism

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