science - chemical effects of electric current

Class 8 - Science

Chemical Effects of Electric Current

Q&A
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Question:
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?
Answer:

Copper ion is positively charged. It is attracted towards the plate which is connected to the negative terminal of the battery. As copper ions are transferred to the thin copper plate, this thin pure copper plate must be connected to the negative terminal of the battery. Consequently, impure copper rod is connected to the positive terminal of the battery.

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Questions and Answers


Chemical Effects of Electric Current - Questions
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.
Answer
2. 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?
Answer
3. 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.
Answer
4. The bulb does not glow in the setup. List the possible reasons. Explain your answer.
Answer
5. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer
6. 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?
Answer
7. 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
8. Does pure water conduct electricity? If not what can we do to make it conducting?
Answer
9. Prepare a list of objects around you that are electroplated.
Answer
10. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
Answer
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.
Answer
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