Two circular coils A and B are placed close to each other. If the current in coil A is changed, some current is induced in coil B. Give reason.

When two circular coils A and B are placed close to each other, and the current in coil A is changed, then some current will be induced in coil B. This is because a changing current in coil A produces a changing magnetic field. This changing magnetic field passes through coil B. According to Faraday's law of electromagnetic induction, a changing magnetic field induces an electromotive force (EMF) in a coil. This induced EMF then drives a current in coil B. The magnetic field associated with coil A changes, thus the magnetic field around coil B also changes. This change in the magnetic field lines around coil B induces an electric current in it. This process is known as electromagnetic induction.