Class VIII, CBSE Science
Chapter 14, Chemical Effects of Electric Current
NCERT Solutions of Textbook Chapter Exercise (Important questions only)
Question.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 ____ effect.
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 metallic object, by means of electricity, is called _______.
Solution: (a) acids, bases, salt (b) chemical (c) negative (d) electroplating.
Question.2: When the free ends of a tester are dipped into a solution the magnetic needle shows deflection. Can you explain the reason?
Solution: Electric current produces magnetic effect which causes deflection of the magnetic needle of a compass. So, when the free ends of a tester are dipped into a solution which is a good conductor of electricity, the needle shows deflection.
Question.4: The bulb does not glow in the set-up shown in figure. List the possible reasons. Explain your answer.
Solution: There could be several possible reasons for not glowing of the bulb:
- The bulb may be fused.
- Even after replacing the bulb if it does not glow, then the connection may be loose or faulty.
- Even after checking and repairing the connections if the bulb does not glow that means the solution does not conduct electricity.
Question.6: Does pure water conduct electricity? If not, what can we do to make it conducting?
Solution: NO, pure water does not conduct electricity. Some salt can be added to make it conductor.
Question.8: A child staying in a coastal region tests the drinking water and also the sea water with his tester. He finds that his tester needle deflects more in case of sea water. Can you explain the reason?
Solution: Drinking water has been processed and purified before supplying to the houses. Many salts and minerals have been removed from it, which will reduce its electricity conducting property considerably. On the other hand the sea water is rich in salts, and other acids and basic substances, that is why is a better conductor of electricity and deflects the needle more than the purified drinking water.
Also study - Additional important questions on Chapter 14, NCERT Science