When the free ends of a conductivity tester (made by using a battery connected to a wire wound around a compass) are dipped into a solution, the magnetic needle shows deflection. Can you give the reason for this deflection.

Because the free ends of a conductivity tester are dipped into a conducting solution then, it behaves like a current carrying wire and a current carrying wire behaves as a magnet because it produces magnetic field around it. And, due to this there is deflection in the compass.