A bar magnet is placed on a sheet of graph paper and twelve magnetic field lines…
PHYSICS · Multi-part · CBSE · Physics · Magnetism and Matter · Magnetism and Matter
Problem
A bar magnet is placed on a sheet of graph paper and twelve magnetic field lines emerging from its north pole are traced using a compass needle. Measurements show that along the equatorial line of the magnet the average spacing between two adjacent field lines is 2 mm at a point 2 cm from the north pole, whereas the spacing increases to 6 mm at a point 6 cm from the same pole.
(i) Draw an approximate field diagram incorporating the above data.
(ii) If the magnetic field strength at any point is inversely proportional to the average spacing between the field lines there, calculate the ratio of the magnetic field strength at 2 cm to that at 6 cm from the north pole along the equatorial line.
(iii) Explain briefly how your answer to part (ii) supports the statement that the magnetic field strength of a bar magnet decreases with distance from the magnet.
(iv) Another identical bar magnet is now placed with its south pole facing the north pole of the first magnet at a separation of 1 cm. Predict qualitatively how the field pattern and the spacing between field lines in the region midway between the two facing poles will change. Give reasons for your prediction.