A U-shaped permanent magnet has a 1.5 cm wide air gap between its two poles
PHYSICS · Multi-part · CBSE · Physics · Magnetic Effects of Electric Current · Magnetic Effects of Electric Current
Problem
A U-shaped permanent magnet has a 1.5 cm wide air gap between its two poles. In a student’s sketch of its magnetic field, 30 field lines are found to pass perpendicularly through a rectangular area of 5cm2 located inside the gap, while only 6 field lines pass perpendicularly through an identical area situated 3 cm outside the magnet.
(i) Draw the magnetic field pattern of the U-shaped magnet, clearly showing the regions of strongest and weakest field.
(ii) Assuming that the magnetic field strength is directly proportional to the number of field lines per unit area, calculate the ratio of the magnetic field strength inside the gap to that outside the magnet.
(iii) State any two practical consequences of the high magnetic field inside the gap of a U-shaped magnet.