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b) By using a Magnetic Compass:

 We can also detect weak electric current flowing through a liquid using a magnetic

compass, by making use of magnetic effect of electric current.
 Take out the cardboard tray from the inside of a discarded matchbox.

 Place the compass inside the cardboard tray.
 Wrap an electric wire a few times around the cardboard tray, so as to make a type of

coil of wire around the compass.
 Here, for testing the wrapped cardboard tray along with the compass is used instead

of electric bulb.

 The two ends of the wrapped electric wire is attached an electric source.
 Even if a weak electric current flows through the liquid in the circuit, the

magnetic needle of compass will show deflection.
 This is because, even a weak electric current flowing through a wire produces a

magnetic field around it and this magnetic field of electric current acts on the

magnetic needle and deflects it from its usual north-south direction.
 So, if a compass surrounded by a wound up electric wire of a circuit including

a liquid in it shows deflection, it will mean that the liquid conducts electricity.

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