Physics
Physics
Problem
A north pole of a bar magnet is moved rapidly towards the centre of a circular coil lying in its plane and facing the magnet. When viewed from the magnet side, in which direction will the induced current circulate in the coil? a) Clockwise b) Anticlockwise c) No current is induced d) Direction keeps reversing continuouslyIntuitive explanation
The key is Lenz's law: the induced current always opposes the change causing it. As the north pole approaches, the magnetic flux through the coil increases, so the induced current must create its own magnetic field pointing away from the approaching north pole—meaning the coil acts like a north pole to repel it. Using the right-hand rule, if your thumb points outward (away from the magnet), your fingers curl in the direction of current flow. When viewed from the magnet side, that's counterclockwise.
Intuitive explanation
The key is Lenz's law: the induced current always opposes the change causing it. As the north pole approaches, the magnetic flux through the coil increases, so the induced current must create its own magnetic field pointing away from the approaching north pole—meaning the coil acts like a north pole to repel it. Using the right-hand rule, if your thumb points outward (away from the magnet), your fingers curl in the direction of current flow. When viewed from the magnet side, that's counterclockwise.