Question

When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Give reasons for the observation.

Answer 1

Hint: Magnetic needle will show deflection in presence of an electric or magnetic field.
When an electric current passes through a conductor, a magnetic field is produced. This magnetic field exerts a force on the magnetic needle. This force causes deflection.

Complete answer:
An electric current will flow when the circuit is complete. But if the circuit is broken, electric current will not flow. When the circuit is complete, a magnetic field is generated, which causes deflection of the magnetic needle.
When you dip the free ends of a tester into a solution, the magnetic needle shows deflection. This is due to the flow of electricity.
When you dip the free ends of a tester into a solution, ions present in the solution move from one terminal to another terminal. Flow of ion results in flow of an electric current.
Due to the flow of an electric current, a magnetic field is produced. This magnetic field causes the deflection of the magnetic needle.

Thus, when ions flow, electric current flows, a magnetic field is generated and a magnetic needle is deflected.

Note: If the solution is not a conducting solution, then no deflection of the magnetic needle will be observed, even if the free ends of a tester are dipped into a solution. This is because a non conducting solution does not conduct electricity, as it does not contain current carrying ions. If no electric current flows, then no magnetic field will be produced. Hence, there will be no deflection of the magnetic needle.