Chemical Effects of Electric Current Question Answers: NCERT Class 8 Science

(a) Acids and bases, salts

Some of the acidic, basic and neutral solutions also conduct electricity. They allow the current to pass through them.

(b) Chemical

When current passes through a solution, it dissociate into ions, i.e. positive and negative ions. The process of decomposition of the solution is called as chemical effect.

(c) Negative

The solution dissociate into positively charges copper ions and negatively charged sulfate ions, when we pass electricity or current through a copper sulfate solution. Positively charged copper ions attached to plate which is connected to the negative terminal of the battery.

(d) Electroplating

Electroplating is done on metals, to prevent them from the rusting with the help of electricity.

Rain water contains a large amount of impurities like acids, minerals etc. which makes the rain water a good conductor of electricity and the compass needle shows deflection.

1. Chromium plating is done on many objects such as car parts, bath taps, kitchen gas burners and many others.
2. Jewellary makers electroplate silver and gold on expensive metals.
3. Tin cans used for storing food that are made by electroplating tin onto iron.
4. Iron is used in bridges automobiles to provide strength. That’s why a coating of zinc is deposited on iron to protect it from corrosion and from the formation of rust.

The thin plate of pure copper is connected to the negative terminal of the battery to make it cathode, while the thick rod of impure copper is connected to the positive terminal of the battery to make it anode; because the copper forms positive ions which are attracted to the electrode and connected to the negative terminal of the battery and gets deposited over it. 

This is due to the magnetic effects of the electric current. When the free ends of the tester are dipped into the solution, the circuits get completed and the current starts flowing through it. And, then the current carrying conductor behaves like a magnet. Hence, magnetic needle shows the deflection.

Lemon juice (citric acid) C₆H₈O₇, Vinegar (Acetic acid) H₃COOH, Hydrochloric acid (HCl), salt (NaCl). Because these solutions allow electricity to pass through them.

The bulb may not glow in the given setup due to the following reasons:

1. The liquid may not contain ions or charged particles.
2. The bulb may be fused.
3. Cells which are used in the battery may be used up.
4. The connecting wire may be broken up.
5. Connection may be loose.

(i) Liquid A is better conductor than liquid B

The amount of electric current flowing through a conducting solution always depends on the conductor of the solution. More current can pass through the solution with more conductivity and vice versa. So, the conductivity of liquid A is more than liquid B.

No, pure water does not conduct electricity because pure water does not contain ions to conduct electricity. In order to make it conducting, we should add salt, acid and base in the water. Hence, water conducts electricity.

Because water is a good conductor of electricity. Hence, a fireman may get an electric shock. So, in order to prevent from the electric shock they first shuts off the main electrical supply of that area.

The compass needle deflects more in the case of sea water because it contains a large amount of dissolved salt which makes it a good conductor of electricity than the drinking water.

No, it is not safe because rainy water contains a large amount of (salt) impurities like acids, minerals etc. which makes the rain water a good conductor of electricity and the electrician may get an electric shock.