NCERT Solution For Class 8 Science, Chapter 14 – Chemical Effects of Electric Current

ncert solutions for  science chapter 14 Chemical Effects of Electric CurrentClass 8 Science, Chapter 14 – Chemical Effects of Electric Current

NCERT Solutions is known as an extremely helpful resource for preparing for the exam. Takshila Learning provides its learners with access to a wealth of NCERT problems and their solutions. CBSE Class 8 Science NCERT Solutions are built by subject matter experts, so be sure to train learners for a good grade. The questions set out in the NCERT Books are prepared in compliance with the requirements of the CBSE.

NCERT Solution For Class 8 Science – The Indian Constitution provides us with all-inclusive information on all concepts. As students would have to learn the basics about the subject in class 8, this curriculum for class 8 is comprehensive study material, which explains the concepts in a great way.

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 _________.

 

Solution:

 

  1. 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 them.)

 

(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.

 

 

Q2. When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?

 

Solution:

The deflection within the compass needle shows that current is flowing through the wire and hence, through the circuit. The circuit is complete since free ends of the tester are dipped during a solution. The answer is a conducting solution.

Q3. Name three liquids, which when tested in the manner shown in Fig. 14.9, may cause the magnetic needle to deflect.

 

Solution:

Liquids like lime juice, salt water and mercury allow electricity to undergo them. Hence, these liquids are often used as within the beaker to point out the given effect.

 

Q4. The bulb does not glow in the setup shown in Fig. 14.10. List the possible reasons. Explain your answer.

 

Solution:

The bulb might not glow due to the subsequent reasons:

 

(i)         Liquid within the beaker is non-conducting. In such case, the electrical current wouldn’t be ready to undergo the liquid. Hence, the circuit isn’t complete.

 

(ii)        Electric current within the circuit is extremely weak. This can happen if the material used for creating the circuit isn’t a good conductor of electricity or the battery doesn’t have sufficient energy to induce electricity.

 

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.

 

Solution:

(i) Liquid A is a better conductor than liquid B.

 

The amount of current flowing through a conducting solution depends on the conductivity of the material. With more conductivity, more current passes through the answer and vice-versa. Hence, the conductivity of liquid A is over the conductivity of liquid B.

 

Q6. Does pure water conduct electricity? If not, what can we do to make it conducting?

 

Solution:

No. Pure water doesn’t conduct electricity as pure water is devoid of any salts. Pure water can conduct electricity when a pinch of common salt is added to it, as salt solution is conducting in nature.

 

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.

 

Solution:

Water may conduct electricity. If the electrical supply for the realm isn’t shut off and water is poured over electrical appliances, then electricity may touch water and harm the firemen.So, the firemen shut off the most electrical supply for the realm before they use the water hoses.

 

Q8. 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?

 

Solution:

Sea water contains more dissolved salts than the beverage. Hence, it’s more conducting than the beverage. Due to this reason, the compass needle deflects more in seawater than in the beverage.

 

Q9. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.

 

Solution:

No. It is not safe to repair electrical appliances outdoors during heavy downpour as rain water contains dissolved salts. Therefore, rain water can conduct electricity. The electrician may get electrical shocks while working outdoors during rain.

 

Q10. 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?

 

Solution:

Rain water contains dissolved salts. This makes it a conducting solution. There aren’t any dissolved salts present within the H2O. Hence, rain water can allow electricity to pass through it while H2O cannot.

 

Q11. Prepare a list of objects around you that are electroplated.

 

Solution:

Examples of electroplated objects are as follows:

 

(i)         Chromium plating is done on different parts of cars, buses and motor cycles to give them shiny appearance.

 

(ii)        A fine layer of gold is deposited on the silver ornaments and are called gold-plated ornaments.

 

(iii)       Iron employed in constructing a building is coated with a layer of zinc to protect iron from corrosion and rusting.

 

Q12. 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?

 

Solution:

Copper ion is positively charged. It’s attracted towards the plate which is connected to the negative terminal of the battery. As copper ions are transferred to the skinny 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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