NCERT Class VIII Science Solutions: Chapter 14-Chemical Effects of Electric Current Part 2

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Question 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

  1. Liquid A is a better conductor than liquid B.

  2. Liquid B is a better conductor than liquid A.

  3. Both liquids are equally conducting.

  4. Conducting properties of liquid cannot be compared in this manner.

Answer:

A. Liquid A is a better conductor than liquid B.

Question 6:

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

Answer:

Pure or distilled water does not contain salts. Therefore it is a poor conductor of electricity. We can add impurities like salt, lemon juice, vinegar etc. to make it conducting.

Result for images is a conduct electricity

Conduct Electricity

Question 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.

Answer:

The water usually contain salts and is a good conductor of electricity. To save themselves and others from electric shock and to avoid any short circuit, firemen shut off the main electrical supply for the area.

Question 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?

Answer:

Drinking water is chemically treated and purified by removing various impurities and salts from it. While the sea water contains lots of mineral salts. Therefore, sea water produce more ions (more electric charges) as compared to drinking water and the child sees more deflection in magnetic needle in case of sea water.

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