The materials which allow electric current to pass through them are good conductors of electricity, on the other hands which do not allow electric current to pass through them easily are poor conductors of electricity.
Insulator: Substances which do not allow electric current to pass through them are called insulators; such as plastic, rubber, etc.
Tester
It is a device to test if a particular material allows electric current to pass through it or not.
DO LIQUIDS CONDUCT ELECTICITY?
- A tester could be used to check if a liquid allows electric current to pass through it or not i.e. conducting or non-conducting.
- To check conductivity, connect the liquid between the two ends of tester.
- When the liquid between the two ends of the tester allows the electric current to pass, the circuit of the tester becomes complete.
- If bulb in the tester glows, it means the liquid is conducting.
- Most liquids that conduct electricity are solutions of acids, bases and salts.
To test if substance is conducting or not using heating effect
When current passes through the bulb, the filament gets heated to a high temperature and as a result bulb starts glowing. But, if current is very small then the filament will not get heated to a high temperature and so will not glow.
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LED (Light Emitting Diodes)
LED’s can be used to detect weak currents, as their filament does not require much temperature to glow.
They have two terminals called anode and cathode.
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Tap Water-The water obtained from various sources contains many impurities in it like rivers, wells, taps, etc. is not in its purest form. It includes different salts. As a result of these salts, the tap water becomes a good conductor of electricity.
Distilled Water-It is the purest form of water and does not contain any kind of impurities in it. Hence, it is a poor conductor of electricity.
CHEMICAL EFFECTS OF ELECTRIC CURRENT
- The passage of electric current through a conducting solution causes chemical reactions.
- Electrodes-These are conducting materials through which current enters or leaves a substance.
SOME EFFECTS
- Formation of Gas Bubbles
if current is passed through water, then, bubbles of oxygen and hydrogen were produced. The passage of an electric current through a conducting solution causes chemical reactions. As a result, bubbles of a gas may be formed on the electrodes
- Deposits of metal may be visible on the electrodes.
- The colour of solution might change.
ELECTROPLATING
The process of depositing a layer of any desired metal on another material by means of electricity is known as electroplating.
Example/experiment- let us take copper sulphate and two copper plates of same size. Take 250 mL of distilled water in a clean and dry beaker. Dissolve two teaspoonfuls of copper sulphate in it. Add a few drops of dilute sulphuric acid to copper sulphate solution to make it more conducting. Connect the copper plates to the terminals of a battery and immerse them in copper sulphate solution.
- When current is passed through the copper sulphate solution, then copper sulphates dissociates into copper and sulphate.
- The free copper of the solution will get deposited on the negative electrode.
- The equal amount of copper gets dissolved in the solution from the positive electrode.
- So, we can say that copper from positive electrode got transferred to the negative electrode. This kind of transfer is known as
APPLICATIONS
(Electroplating is a very useful process)
- It is used in industries for coating different metals on other metal objects. For example, chromium plating is done on many objects such as car parts, bath taps, wheel rims and many others lower the manufacturing cost.
- Silver and gold plating is done on less expensive metals keeping the appearance intact.
- Iron cans are electroplated with tin used for storing food, as iron gets easily rusted and so protects the food from spoiling.
- Zinc is deposited on iron used for the construction of bridges, vehicles, etc. to protect it from rust and corrosion.