NCERT Solutions for Class 8 Science Science - NCERT Solution Chapter 14

Chemical Effects of Electric Current Class 8

Chapter 14 Chemical Effects of Electric Current Exercise Solutions

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Exercise : Solutions of Questions on Page Number : 180

Q1 :  

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 _________ effects.

(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 material by means of electricity is called _________.


Answer :

(a) Most liquids that conduct electricity are solutions of __acids__, __bases__ and __salts__.

(The solutions of acids, bases or salts are conducting in nature. They allow the current to pass through.)

(b) The passage of an electric current through a solution causes __chemical__ effects.

(When an electric current passes through a solution, the solution decomposes into its positive and negative ions. This process of decomposition of the solution is a chemical effect.)

(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the __negative__ terminal of the battery.

(When an electric current passes through a copper sulphate solution, the solution decomposes into positively charged copper ions and negatively charged sulphate ions. These positively charged copper ions get attracted towards the plate which is connected to the negative terminal of a battery.)

(d) The process of depositing a layer of any desired metal on another material by means of electricity is called __electroplating__.

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Q2 :  

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


Answer :

The deflection in the compass needle shows that current is flowing through the wounded wire and hence, through the circuit. The circuit is complete since free ends of the tester are dipped in a solution. The solution is certainly a conducting solution. This is the reason why the compass needle shows a deflection.

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Q3 :  

Name three liquids, which when tested in the manner shown in Fig. 14.9, may cause the magnetic needle to deflect.


Answer :

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Q4 :  

The bulb does not glow in the setup shown in Fig. 14.10. List the possible reasons. Explain your answer.


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Q5 :  

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.


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Q6 :  

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


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Q7 :  

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.


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Q8 :  

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.


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Q9 :  

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?


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Q10 :  

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


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Q11 :  

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?


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Q12 :  

Prepare a list of objects around you that are electroplated.


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Q13 :  

The process that you saw in Activity 14.7 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?


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<< Previous Chapter 13 : Sound Next Chapter 15 : Some Natural Phenomena >>

Science - NCERT Solution - Science : CBSE NCERT Exercise Solutions for Class 8th for Chemical Effects of Electric Current will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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