Science

Chemical Effects of Electric Current

Question:

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:

Water may conduct electricity. If the electrical supply for the area is not shut off and water is poured over electrical appliances, then electricity may pass through water and harm the firemen. That is why, in case of a fire, the firemen shut off the main electrical supply for the area before they use the water hoses.
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Chemical Effects of Electric Current

Q 1.

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.

Q 2.

Name three liquids, which when tested in the manner, may cause the magnetic needle to deflect.NCERT Solutions for Class 8th Science Chapter 14 Chemical Effects of Electric Current.

Q 3.

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

Q 4.

The process that is used for purification of copper. A thin 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?

Q 5.

Paheli had heard that rain water is as good as distilled water. So, she collected some rain water 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 reasons?

Q 6.

The bulb does not glow in the setup. List the possible reasons. Explain your answer.

Q 7.

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

Q 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?

Q 9.

Prepare a list of objects around you that are electroplated.

Q 10.

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

Q 11.

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.