NCERT Grade 8-Chemical Effect of Electric Current-Questions

NCERT Solutions for Class 8 Science

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Chemical Effect of Electric Current

Exercise 1

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 ______.

2.    When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

3.    Name three liquids, which when tested in the manner shown in Fig. may cause the magnetic needle to deflect.

4.    The club does not glow in the setup shown fig. List the possible reasons. Explain your answer.

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.

6.    Does pure water conduct electricity? If not, what can we do to make it conducting?

7.    In case of fire, before the firemen use the water hoses, they shut off the main electric supply for the area. Explain why they do this.

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?

9.   Is it safe for the electrician to carry out electrical repairs outdoors during heavy rain pour? Explain.

10.  Paheli had heard that rainwater is as good as distilled water. So, he collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reason?

11.   Prepare a list of objects around you that are electroplated.

12.  The process that you saw in Activity 14.7 is used for purification of copper. A this plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?

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