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Physics · 2025 · 3 marks
CBSE 2025 · Region 4 · Set 2 · Q24
(a) Differentiate between magnetic flux through an area and magnetic field at a point. (b) A bar magnet is held with its length along the axis of a…
(a)
Differentiate between magnetic flux through an area and magnetic field at a point.
(b)
A bar magnet is held with its length along the axis of a closed coil. Initially the south pole of the magnet faces the coil. If the magnet is moved towards the coil, explain how a current is induced in the coil and in what direction.
Marking-scheme solution
(a)
Magnetic flux is equal to the total number of magnetic field lines passing normal to the given area.
Magnetic field at a point is the region in the space around the magnet or moving charge where magnetic force can be experienced.
(b)
When the south pole of the bar magnet moves closer to the coil, the magnetic flux through the coil increases. Hence according to Faraday's law an induced emf/current is generated in the coil.
According to Lenz's law the near end of the coil becomes a south pole and as a consequence the current in the coil flows in the clockwise direction.
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