Chemical Effects of Electric Current class 8 questions and answers: Science Class 8 chapter 11 question answer
| Textbook | Ncert |
| Class | Class 8 |
| Subject | Science |
| Chapter | Chapter 11 |
| Chapter Name | Chemical Effects of Electric Current ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Class 8 Science chapter 11 question answer? Now you can download ncert solutions for class 8 science chapter 11 pdf from here.
Question 1: 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 1: (a) Most liquids that conduct electricity are solutions of acids, bases and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
Question 2: When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
Answer 2: The compass needle shows a deflection, which concludes that current is flowing through the wire. The circuit becomes complete as the free ends of the tester are immersed inside the solution. So, the solution is conducting solution; hence, deflection is obtained in the compass needle.
Question 3: Name three liquids, which when tested in the manner shown in Fig.11.9, may cause the magnetic needle to deflect.
Answer 3: Liquids such as lemon juice, saltwater, and vinegar are conducting liquids that allow electricity to pass through them. Hence, these liquids can be used in the beaker to show the deflection of the magnetic needle.
Question 4: The bulb does not glow in the setup shown in Fig.11.10. List the possible reasons. Explain your answer
Answer 4: The bulb may not glow because of the following reasons:
- (i) The wires in the circuit may be loosely connected.
- (ii) The bulb may be fused.
- (iii) The cells may be used up.
- (iv) The liquid may be an insulator, i.e., a poor conductor of electricity.
Question 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.
Answer 5: (i) liquid A is a better conductor than liquid B.
Question 6: Does pure water conduct electricity? If not, what can we do to make it conducting?
Answer 6: No, pure water doesn’t conduct electricity. But when salt is dissolved in pure water, it conducts electricity.
Question 7: 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 7: 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.
Question 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?
Answer 8: The amount of dissolved salts present in the seawater is more than the water we use for drinking purposes. As a result, seawater will conduct electricity better than drinking water. So, the compass needle shows more deflection in seawater than in drinking water.
Question 9: Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
Answer 9: No. Repairing electrical items outside during prolonged downpours is not safe. Rainwater is conductive because it contains a specific proportion of dissolved salts. When an electrician works outside during a prolonged downpour, this could result in electric shocks and injury.
Question 10: Paheli had heard that rainwater is as good as distilled water. So she collected some rainwater 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 10: Rainwater is pure water which is an insulator but it gets mixed with air pollutants like sulphur dioxide and nitrogen oxides and form acidic solution, which is a good conductor of electricity. So, the compass needle showed deflection.
Question 11: Prepare a list of objects around you that are electroplated.
Answer 11: Here are some common electroplated objects around us:
- Gas Stove Burners – Nickel-plated for durability.
- Cutlery – Spoons, forks, and knives (silver-plated).
- Jewelry – Gold or silver-plated ornaments.
- Bathroom Fixtures – Faucets and showerheads (chrome-plated).
- Car Parts – Bumpers and rims (chrome-plated).
- Electronic Connectors – Gold-plated USB and charging ports.
- Coins – Some coins have electroplated layers.
- Watches – Gold or rhodium-plated cases.
- Eyeglass Frames – Nickel or gold-plated.
- Door Handles – Chrome or brass-plated.
Question 12: The process that you saw in Activity 11.7 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 transfered to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
Answer 12: 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.