Chapter 14
Chemical Effects of Electric Current
1. Fill in the blanks.
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___________terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called _________.
Ans:
(a) acids, bases, salts
(b) chemical
(c) negative
(d) electroplating
2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Ans:
The deflection in magnetic needle shows that the solution is a good conductor of electricity.
3. Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ___________terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called _________.
Ans:
(a) acids, bases, salts
(b) chemical
(c) negative
(d) electroplating
2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Ans:
The deflection in magnetic needle shows that the solution is a good conductor of electricity.
3. Name three liquids, which when tested in the manner shown in Fig.14.9, may cause the magnetic needle to deflect.
Ans:
Vinegar, lemon juice and tap water.
4. The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.
Vinegar, lemon juice and tap water.
4. The bulb does not glow in the setup shown in Fig.14.10. List the possible reasons. Explain your answer.
Ans:
The bulb may not glow because of the following reasons:
(i) The wires in the circuit may be loosely connected.
(ii) The bulb may be fused.
(iii) The cells may be used up.
(iv) The liquid may be poor conductor of electricity.
5. A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
Ans:
(i) liquid A is a better conductor than liquid B.
6. Does pure water conduct electricity? If not, what can we do to make it conducting?
Ans:
No, pure water doesn’t conduct electricity. But when salt is dissolved in pure water, it conducts electricity.
7. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.
Ans:
The water used in the water hoses is a good conductor of electricity. So, the firemen shut off the electric supply before spraying water to save themselves and other people from electric shock.
8. A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
Ans:
The seawater contains more salts in comparison to drinking water, hence the seawater is a better conductor of electricity and it produces a stronger magnetic field in the wire and hence deflects the compass needle more.
The bulb may not glow because of the following reasons:
(i) The wires in the circuit may be loosely connected.
(ii) The bulb may be fused.
(iii) The cells may be used up.
(iv) The liquid may be poor conductor of electricity.
5. A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
Ans:
(i) liquid A is a better conductor than liquid B.
6. Does pure water conduct electricity? If not, what can we do to make it conducting?
Ans:
No, pure water doesn’t conduct electricity. But when salt is dissolved in pure water, it conducts electricity.
7. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.
Ans:
The water used in the water hoses is a good conductor of electricity. So, the firemen shut off the electric supply before spraying water to save themselves and other people from electric shock.
8. A child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
Ans:
The seawater contains more salts in comparison to drinking water, hence the seawater is a better conductor of electricity and it produces a stronger magnetic field in the wire and hence deflects the compass needle more.