Question

In wch of these current is not conducted by electrons?1-copper 2- murcury 3- aluminium 4-tap water

Answer 1

Mercury is the answer

Answer 2

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Your elders might haan 1 cm apart but at the same time do not touch each other. Does the bulb of the tester glow? Does lemon juice or vinegar conduct electricity? How wouasses through it? Due to the heating effect of current, the filament of the bulb gets heated to a high temperature and it starts glowing. However, if the current through a circuit is too weak, the filament does not get heated sufficiently and it does not glow. And why is the current in the circuit weak? Well, though a material may conduct electricity, it may not conduct it as easily as a metal. As a result, the circuit of the tester may be complete and yet the current through it may be too weak to make the bulb glow. Can we make another tester which can detect a weak current?

You may use an LED (Fig. 3) in place of the electric bulb in the tester of Fig. 2. LED glows even when a weak electric current flows through it. There are two wires (called leads) attached to an LED. One lead is slightly longer than the other. Remember that while connecting to a circuit, the longer lead is always connected to the positive terminal of the battery and the shorter lead is connected to the negative terminal of the battery.

Fig.3 LEDs

We can use another effect of an electric current to make another kind of tester. Do you recall that electric current produces a magnetic effect? What happens to a compass needle kept nearby when current flows in a wire? Even if the current is small, the deflection of the magnetic needle can be seen. Can we make a tester using the magnetic effect of currents? Let us find out.

Activity 3Take the tray from inside a discarded matchbox. Wrap an electric wire a few times around the tray. Place a small compass needle inside it. Now connect one free end of the wire to the terminal of a battery. Leave the other end free. Take another piece of wire and connect it to the other terminal of the battery (Fig. 4).
Fig.4 Another testerJoin the free ends of two wires momentarily. The compass needle should show deflection. Your tester with two free ends of the wire is ready.Now repeat Activity 2 using this tester. Do you find a deflection in the compass needle the moment you dip the free ends of the tester in lemon juice?
Fig.8 Some electroplated objects

Tin cans, used for storing food, are made by electroplating tin onto iron.