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NCERT Solutions Class 8 Science Chapter 11 Chemical Effects of Electric Current
You might have noticed a warning sign near electrical poles during rainy days, advising people to stay away. But do you know why it's risky to go near electrical poles when it's raining? You will get all the answers related to electric current and its properties in NCERT Solutions for Class 8 - Science chapter chemical effects of electric current, which focuses on chemical changes that can be produced by passing electric current through different types of materials and substances.
To comprehend class 8 chemical effects of electric current concepts well, one must practice questions regularly with chemical effects of electric current class 8 question answer. Chemical effects of electric current class 8 solutions are given for all the questions in the textbook which increases problem-solving skills and also boosts confidence.
1.0Download NCERT Solutions for Class 8 Science Chapter 11 : Free PDF
Solving NCERT Solutions for class 8 science chapter 11 will help students to analyze in which areas they are weak and need to improve in order to get good marks in the final exam. Students also get to know the type of questions which can be asked from various topics in science class 8 chemical effects of electric current and often some questions do come from the NCERT textbook only.
2.0NCERT Questions with Solutions Class 8 Science Chapter 11 - Detailed Solution
- 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 (a) Acids; bases ; salts (b) Chemical (c) Negative (d) Electroplating
- 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 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.
- Name three liquids, which when tested in the manner shown in figure, may cause the magnetic needle to deflect.
- Solution Liquids like salt water, lemon juice and sodium hydroxide solution allow electricity to pass through them. Hence, these liquids can be used as in the beaker to show the given effect.
- The bulb does not glow in the setup shown in figure List the possible reasons. Explain your answer.
- Solution The bulb may not glow because of the following reasons: (i) Liquid in the beaker is nonconducting. In such case, the electric current would not be able to pass through the liquid. Hence, the circuit is not complete. (ii) Electric current in the circuit is very weak. This can happen if the material used for making the circuit is not a good conductor of electricity or the battery does not have sufficient energy to generate electricity.
- A tester is used to check the conduction of electricity through two liquids, labelled A and . It is found that the bulb of the tester glows brightly for liquid while it glows very dimly for liquid B. You would conclude that (i) liquid A is a better conductor than liquid . (ii) liquid B is a better conductor than liquid . (iii) both liquids are equally conducting. (iv) conducting properties of liquid cannot be compared in this manner. Solution Option (i) is correct i.e., liquid A is a better conductor than liquid . The amount of current flowing through a conducting solution depends on the conductivity of the solution. With more conductivity, more current passes through the solution and vice-versa. Hence, the conductivity of liquid is more than the conductivity of liquid .
- Does pure water conduct electricity? If not, what can we do to make it conducting? Solution No. Pure water does not conduct electricity. This is because pure water is devoid of any salts. Pure water can conduct electricity when common salt, an acid (like ) or a base (like NaOH ) is added to it, as these solutions are conducting in nature.
- 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 Ordinary water conducts 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.
- A child staying in a coastal region tests the drinking water and also the sea water with his tester. He finds that the compass needle deflects more in the case of sea water. Can you explain the reason? Solution Sea water contains more dissolved salts than the drinking water. Hence, it is more conducting than the drinking water. Because of this reason, the compass needle deflects more in sea water than in the drinking water.
- 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. This is because rain water contains dissolved salts. Therefore, rain water can conduct electricity. The electrician may get electrical shocks while working outdoors during rain.
- 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? Solution As rain drops fall through the air, they may dissolve ions present in air or forming acids on reaction with acidic oxides present in air, etc. This makes it a conducting solution. There are no dissolved salts present in the distilled water. Hence, rain water can allow electricity to pass through it while distilled water cannot.
- 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 they are called gold-plated ornaments. (iii) Iron used in constructing a building is coated with a layer of zinc. This protects iron from corrosion and rusting.
- The process that you saw in (active physics 8) 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 battery and why? Solution 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 (see figure given below). Reactions that take place in this process are : (i) At cathode (negative copper plate) : (Reduction of Cu ) The Cu atoms so produced get deposited on the cathode. (ii) At anode (positive copper plate) (oxidation of Cu )
- (Purification of copper)
3.0What Will Students Learn in Chapter 11: Chemical Effects of Current?
- The concept of electric current and how it affects liquids.
- How liquids can conduct electricity and the factors that influence this.
- The process of electrolysis and its applications.
- Real-life uses of the chemical effects of electric current, like electroplating and electrorefining.
- The dangers of electric shocks and safety measures for handling electrical devices with wet hands.
These topics provide a practical understanding of how electric current interacts with different materials.