Chemical effect of electric current of Class 8
Electrical conductivity is a measure of the ability of a substance to carry electric current. Substances that are good conductors of electricity have high electrical conductivity as compared to substances that are poor electrical conductors (also called insulators). Same liquids, but not all, are also good conductors of electricity.
CONDUCTIVITY OF WATER:
Pure water is a poor conductor of electricity. But the water that we use in our houses is not pure water. Generally, water (tap water, pond water, well water, etc.) contains a lot of impurities, most of which are usually dissolved salts. The presence of even a small amount of impurity makes water a good conductor of electricity.
Touching an electrical appliance with wet hands could therefore, be dangerous.
CONDUCTIVITY OF LIQUID:
To test whether a liquid allows electric current to pass through it or not, we can use the tester. When the liquid between the two ends of the tester allows the electric current to pass, the circuit of the tester becomes complete. The current flows in the circuit and the bulb glows. When the liquid does not allow the electric current to pass, the circuit of the tester is not complete and the bulb does not glow.
In some situations even though the liquid is conducting, the bulb may not glow. 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. 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.
Most liquids that conduct electricity are solutions of acids, bases and salts.