CBSE 8th Standard Science Chemical Effects of Electric Current Important Questions And Answers Study Material - QB365 Set C | QB365

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CBSE 8th Standard Science Chemical Effects of Electric Current Important Questions And Answers Study Material - QB365 Set C

Published on: 29/10/2025

Question Set C

CBSE 8th Standard Science Chemical Effects of Electric Current Important Questions And Answers Study Material - QB365

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Std: 8th Standard CBSE - Science

chapter: Chemical Effects of Electric Current - Important Questions And Answers

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Questions:

Multiple Choice Question

15 x 1 = 15

Boojho's uncle has set up an electroplating factory near his village. He should dispose off the waste of the factory

(a)

in the nearby river

(b)

in the nearby pond

(c)

in the nearby corn field

(d)

according to the disposal guidelines of the local authority

The process of depositing a thin layer of any superior metal over an object of a cheaper metal with the help of electricity is called

(a)

electro refining

(b)

electro-metallurgy

(c)

electroplating

(d)

None of the above

Boojho and Paheli performed experiments taking similar bulbs and cells but two different solutions A and B as shown in figure.

They found that the bulb in the set up A glows more brightly as compared to that of the set up B. You would conclude that

(a)

higher current is flowing through the circuit in set up A

(b)

higher current is flowing through the circuit in set up B

(c)

equal current is flowing through both the circuits

(d)

the current flowing through the circuits in the two set ups cannot be compared in this manner

Which of the following solutions will not make the bulb glow in figure?

(a)

Sodium chloride

(b)

Copper sulphate

(c)

Silver nitrate

(d)

Sugar solution in diluted water

The device which can be used to detect very small current flowing in an electric circuit is

(a)

LEAD

(b)

MCB

(c)

LED

(d)

None of these

The presence of a small amount of impurities makes water

(a)

a good conductor of electricity

(b)

a bad conductor of electricity

(c)

pure

(d)

None of the above

Which one of the following solutions will not conduct electricity

(a)

Lemon juice

(b)

Vinegar

(c)

Tap water

(d)

Vegetable oil

The solution that can conduct electricity is of

(a)

pure water

(b)

water and acid solution

(c)

water and salt solution

(d)

Both (b) and (c)

An electrolyte is

(a)

a metal

(b)

a solution

(c)

a liquid that conducts current

(d)

All of the above

10.

When electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates

(a)

the chemical effect of current

(b)

the heating effect of current

(c)

the magnetic effect of current

(d)

the lightning effect of current

11.

Electrolytes conduct electricity due to the movement of

(a)

electrodes

(b)

atoms

(c)

electrons

(d)

ions

12.

Plastic wire is

(a)

an insulator

(b)

a conductor

(c)

Both (a) and (b)

(d)

None of these

13.

On passing electric current through solution of an electrolyte, the solution experiences

(a)

magnetic effect

(b)

heating effect

(c)

chemical effect

(d)

None of these

14.

An electric current can produce

(a)

heating effect

(b)

chemical effect

(c)

magnetic effect

(d)

chemical, heating and magnetic effects

15.

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

(a)

liquid A is a better conductor than liquid B

(b)

liquid B is a better conductor than liquid A

(c)

both liquids are equally conducting

(d)

conducting properties of liquid cannot be compared in this manner

Generic 3

5 x 3 = 15

16.

State the reason, why do we need magnetic compass to test the conduction of electric current.

17.

State some advantages of electroplating

18.

Explain in brief the procedure of glowing of bulb in a liquid

19.

Boojho made the circuit as shown in figure. He wanted to observe what happens when an electric current is passed through water. But he forgot to add a few drops of lemon juice to water. Will it make any difference to his observations? Explain

20.

Name three liquids which when tested in the manner shown in figure below may cause the magnetic needle to deflect.

Generic 2

5 x 2 = 10

21.

What happens when common salt is added to distilled water?

22.

What is LED?

23.

Give any two examples of liquid conductor

24.

Mention whether the distilled water conducts the electricity or not.

25.

Explain, why is a layer of zinc coated over iron.

Generic 5

2 x 5 = 10

26.

One day Ram was performing and experiment. He was trying to design an electric circuit in which he included tester, bulb and a battery. He had so much eagerness regarding this experiment that in so much hurry, he forgot to take the connecting wires of aluminium. He took the wires without any coating of PVC on them, so it could be dangerous for him. Any how, he managed to design an electric circuit but the moment, he switched ON the circuit, a spark produces and bulb get fused with a small sound. He was about to touch those wires and heated bulb with his bare hands, at the same time, his teacher suggested him to perform the experiment by taking precautions.
(a) Explain, what could be happened, if Ram would touch the electric bulb with his bare hands.
(b) Mention why should he use the aluminium wires in his experiment.
(c) State the values shown by Ram's teacher here.

27.

In the circuit given in the figure, Boojho observed that copper is deposited on the electrode connected to the negative terminal of the battery. Paheli tried to repeat the same experiment. But she could find only one copper plate. Therefore, she took a carbon rod as negative electrode. Will copper be still deposited on the carbon rod? Explain your answer.

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Answers Key:

Multiple Choice Question

15 x 1 = 15

(d)
according to the disposal guidelines of the local authority

(a)
higher current is flowing through the circuit in set up A

(d)
Sugar solution in diluted water

(a)
a good conductor of electricity

(d)
Vegetable oil

(b)
water and acid solution

(b)
a solution

10.

(a)
the chemical effect of current

11.

(d)
ions

12.

(a)
an insulator

13.

14.

(d)
chemical, heating and magnetic effects

15.

(a)
liquid A is a better conductor than liquid B

Generic 3

5 x 3 = 15

16.

Sometimes the bulb does not glow on passing electric current. This is because the electric current flowing through a conductor is so small.So, in case of small current we need magnetic compass to test the conduction.

17.

The advantages of electroplating are given below:
(i) It protects the metal from corrosion and rusting.
(ii) It is used to coat desired metal on other objects.
(iii) It can make more reactive metal like iron.
(iv) Coating of chromium on the metal gives luster to the objects.

18.

If the liquid between the two ends of a tester allows the electric current to pass, then the circuit of the tester becomes complete. The current flow 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

19.

Adding few drops of lemon juice in water will increase the conductivity of the solution. The current will flow in both the cases but adding of lemon juice makes easy the current to flow.

20.

The three liquids are as follows:
(i) Tap water
(ii) HCI or hydrochloric acid
(iii) Sodium hydroxide

Generic 2

5 x 2 = 10

21.

Distilled water is not a good conductor of electricity but adding common salt make it conducting.

22.

LED is a device or bulb which even glows at low or small current.

23.

Tap water, salt solution.

24.

The distilled water does not conduct the electricity.

25.

Layer of zinc is coated over iron because zinc prevents it from rust and corrosion.

Generic 5

2 x 5 = 10

26.

(a) If Ram touched the heated electric bulb, then his hands could get a serious burn and he would not be able to perform the experiment again with the same desire.
(b) Since aluminium is a good conductor of electricity and mostly, it has been seen that aluminium wires are used for performing the experiment instead of wires without having PVC coating on them.
(c) Ram's teacher has a great concern towards Ram, so that he can perform the experiment carefully and can get its fruitful conclusion

27.

Copper will not be deposited on the carbon rod because carbon rod is a poor conductor of electricity. For electroplating, the circuit must be completed and that can be completed only by using the conducting material. Instead of carbon rod, it should be any metal, then only it can be electroplated.