Chapter 37, Problem 25A

Two separate but similar coils of wire are mounted close to each other, as shown below. The first coil is connected to a battery and has a direct current flowing through it. The second coil is connected to a galvanometer. How does the galvanometer respond when the switch in the first circuit is closed? When the current is steady after the switch is closed? When the switch is opened?

To determine

To Explain: The response of the galvanometer when the current is steady, and the switch is closed and open.

Answer to Problem 25A

The galvanometer responds when the switch is opened and closes but not when the current reaches a constant value.

Explanation of Solution

Introduction:

A galvanometer is a device that shows the current flowing in the circuit.

When the switch is closed, current flows in primary coil and a magnetic field generates due to the current. So, there will be a change in the magnetic field linked with the coils. A voltage is induced in the secondary coil due to this change in magnetic field. There will be some deflection in the galvanometer as the current is induced in the secondary coil.

As the current reaches a steady-state, there will no change in the magnetic field associated with the secondary coil and hence, no deflection in the galvanometer.

As the switch is opened, the galvanometer shows deflection but opposite in direction as that of when the switch was closed.

Conclusion:

The galvanometer shows a reading when there is a change in the magnetic field linked with the coil.