Question

When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

Answer 1

The deflection in the compass needle shows that current is flowing through the wound up wire and hence, through the circuit. This shows that the solution is a conducting solution because only then the current can flow through it and hence through the complete circuit. This current through the wound up wire produces a magnetic field around it which acts on the magnetic needle of the compass and deflects it.
Concept insight: A conducting liquid allows electric current to pass through it.