Q7 of 12 Page 182

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.

In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area because 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.


More from this chapter

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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?

 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 downpour? Explain.