Why does a magnetic compass needle pointing North and South in the absence of a nearby magnet get deflected when a bar magnet or a current-carrying loop is brought near it. Describe some salient features of magnetic lines of field concept.
Both the bar magnet or a current carrying loop have their own magnetic field. These external magnetic fields modify the earth’s existing magnetic field. This resultant magnetic field deflects the magnetic compass needle by exerting a magnetic force on it, from its original north-south direction.
Features of magnetic field lines are:
(i) Magnetic field lines represent the magnetic field around the magnetic substance or current carrying conductor. They have both direction and magnitude.
(ii) The field lines emerge from North pole and merge at South pole. Inside the magnet their direction is from south pole to north pole. Hence magnetic field lines are a continuous closed curve.
(iii) The degree of closeness of the field lines is relative to the strength of magnetic field. Strong magnetic field is indicated by crowded field lines or vice versa.
(iv) No two magnetic field lines intersect each other. If they intersect, the compass needle would point towards two different directions at a point, which is impossible.
(v) The parallel and equidistant field lines in a given region indicate the presence of a uniform magnetic field in that region whereas converging or diverging field lines represent the non-uniform magnetic field.