The sea water contains more salts dissolved in it as compared to the tap water. needle the moment you dip the free ends of the tester in lemon juice? Graphite. Jaya sets up a circuit as given below. Answer: Write on the paper with the end of the wire connected to the positive terminal. (a), Question 4. Answer: Allow the current to pass for about 15 minutes. This shows that distilled water does not conduct electricity. Tin is less reactive than iron. The entire NCERT textbook questions have been solved by best teachers for you. It can cause electrocution, as water is a good conductor of electricity. A household uses the following electric appliances: (i) Refrigerator of rating 400 W for ten hours each day. Solution: Question 1. Nickel and chromium-coated articles are used in automobiles and household appliances. Now repeat Activity 14.2 using this tester. In metals electric current is conducted by flow of electrons. Question 3. Conductors : lemon juice, tap water. However, if the bulb does not glow, it means that the tester is not working. No, it is highly dangerous to carry out the electrical repairs outdoors during the heavy downpour. Do you find a deflection in the compass A tester is used to check the conduction of electricity through two liquids, labelled A and B. After removing the electrodes from the solution, we find that copper metal gets deposited on the plate at the negative of the battery. Solution: Answer: [NCT 2011] Give three applications of chemical effect of current. This completes the circuit of the tester and the bulb should glow. Take another piece of wire and connect it to the other terminal of the battery (Fig. (b) The passage of an electric current through a solution causes _______ effects. Record your observations in Table 14.1. (d) chemical energy into magnetic energy Copper from impure rod is sought to be transferred to the thin copper plate. If not, what can we do to make it conducting? Answer: Activity 1 (NCERT Textbook, Page 173) Question 15. Answer: An electric eel is a fish that makes its own electricity ,Lightning is spark of electricity in the air and bulb uses electricity to glow. A tester can be made by attaching one free end of the wire to a terminal of a battery and another wire from other terminal of the battery to a bulb. Explain your answer. This happens because the when current is passed, the K+ ions are attracted to the metal sheet. Answer: Question 3. A cell is an example of conversion of Coal is generally used in thermal power generation which further helps to produce electricity. [NCERT] What is the objective of electroplating ? Activity 4 (NCERT Textbook, Page 175) Answer: Question 11. Collect a few small plastic or rubber caps of discarded bottles and clean them. Chemical Effects of Electric Current Class 8 Extra Questions Higher Order Thinking Skills. After the electroplating of a spoon with silver, it was found that the anode has become thin. Kirchhoff’s Second Law is a consequence of the conservation of energy. --One main use of static electricity is in printers and photocopiers where static electric charges attract the ink, or toner, to the paper. the movement of electrons. (d) semi-insulator First and second cap with acid and base respectively, conducts electricity whereas third cap having sugar dissolved in distilled water do not conduct electricity. Answer: A tester is used to check the conduction of electricity through two liquids, labelled A and B. In liquids, the movement of charged particles (ions) carry current from anode to cathode terminals. Answer: Question 3. The free copper gets deposited on the plate acting as cathode. Test which solutions conduct electricity and which do not. Test. Topics and Sub Topics in Class 8 Science Chapter 14 Chemical Effects of Electric Current: Question 1. 25% of the city of San Francisco's energy is generated by wind power. View and Download PowerPoint Presentations on Electricity And Magnetism Class 8 PPT. Question 4. Classify the following liquids into conductors and insulators : lemon juice, , distilled water, tap water, milk. Explain how it can be used for writing. Take about two teaspoonfuls of distilled water in a clean and dry plastic or rubber cap of a bottle. The iodide ions (I- ) react with starch to turn blue black. (c) negative Can you think of the possible reasons? Good/Poor Conducting Liquids. Can we call the change taking place in the solution a chemical change? Answer: Question 7. Distilled water is a Question 6. All the best! Explain your answer. Yes, the solution does conduct electricity. Electrical energy: The energy produced due to the flow of charge is called electrical energy .it is used widely in electric appliances. Answer: Question 5. Open up your curtains and let the sun shine in! The free copper gets drawn to the plate connected to the negative terminal of the battery and gets deposited on that plate. Question 7. Your tester with two free ends of the wire is ready. Answer: The longer lead (leg) from the LED should be connected to the positive terminal of the battery and the shorter lead to the negative terminal of the battery. The salts separate out and deposit on the sides of the container. Pour one teaspoon of lemon juice or vinegar in one cap. The major uses of electricity and their shares of total electricity use by the commercial sector in 2014 were 2. machine drives (motors)48.2% 3. process heating and boiler use14.4% 4. facility heating, ventilation, air conditioning, and cooling9.5% 5. electrochemical processes6.8% 6. process cooling and refrigeration7.3% 7. lighting6.5% 8. other miscellaneous processes and facility uses7.3% Why ? This steam is used to turn turbines at high speed in a strong magnetic field. Question 2. The lightning conductor used in building protects the building by : Answer: Question 16. Compass needle shows deflection due to magnetic effect of electric current. (c) electrolysis Question 21. Can you ex¬plain the reason? How can you make a tester for testing whether a given material is a conductor or an insulator ? [NCERT]. Liquid B is a better conductor than liquid A. Why is chromium used for electroplating ? Why should you not touch electrical appliances with wet hands ? In each case observe whether the magnetic needle shows deflection or not. (6) Electricity is used to pump underground water from tube wells for irrigation in field. A child staying in a coastal region tests the drinking water and also the seawater with his tester. Question 9. Answer: (a) magnetic energy into chemical energy When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. (iii) both liquids are equally conducting. Question 11. Gravity. as a point source of light in laser beam torches. Question 9. Gradually, a layer of copper builds up on the plate. Join the free ends of two wires momentarily. The electrical resistivity of few materials is given below in ohm-meter. Answer: Does pure water conduct electricity ? When electric current is passed through copper sulphate solution, the copper sulphate breaks up into copper and sulphate ions. Thus, lemon juice, vinegar, tap water, milk, curd and water, and soda are good conductors of electricity while vegetable oil, honey, kerosene oil, and distilled water are poor conductors of electricity or insulators. Answer: Question 10. Question 1. We cannot make the whole article from it because it is a very costly metal. List the possible reasons. What could be the reasons ? resistance 240 = 240 V R= 8 Current (I) = 30 =8A V R= I 39. Question 7. Heat energy: It is the energy due to the motion of molecule. Answer: Question 12. Which of these materials can … This process is known as chemical effects of current. Therefore, we can be electrocuted in case we touch appliances with wet hands. Electric current can produce magnetic effect also. The sum of electric potential differences along any closed loop in a DC circuit is zero. Answer: Liquid A is a better conductor of electricity because the bulb glows more in it. (c) half on the anode and half on the cathode Why? A change in the electric potential change equals the change in electric potential energy per unit charge. Why ? [NCT 2011] (c) cathode These charges can be at rest or moving .Learn how these moving charges constitute current electricity. (a) conduction The process that you saw in Activity 14.7 is used for purification of copper. Answer: How can the magnetic effect be used as a tester ? Name the process of depositing a layer, of any desired metal on another material by means of electricity. Solved Examples for You. A thin plate of pure copper and a thick rod of impure copper are used as electrodes. (d) Nitric acid The rainwater showed deflection with the tester because it is not as pure as distilled water. But when salt is dissolved in distilled water and again tested, the bulb glows which shows that water containing salts conduct electricity. Now connect one free end of the wire to the terminal of a battery. So, the compass needle showed deflection. Electrodes are the terminals through which current is passed into a liquid. It gets deposited on the Is it possible that the connections are loose? In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Answer: Question 12. Answer: Pour a cupful of water in a glass/ plastic bowl. For example, an RV running off of electric heat will use more electricity than an RV running off of propane. As pure water is free of salts and thus it is an insulator so to make pure water conducting, we can add some salts or acid to it. Add a teaspoonful of salt or a few drops of lemon juice to water to make it more conducting. Free PDF Download - Best collection of CBSE topper Notes, Important Questions, Sample papers and NCERT Solutions for CBSE Class 8 Science Chemical Effects of Electrical Current. Method : Question 2. They can produce a shock of around 500 volts. Answer: What is LED? Conducting properties of liquid cannot be compared in this manner. What colour is the coating? Paheli had heard that rainwater is as good as distilled water. In order to make electricity useful, we had to find a way to not only generate large amounts of electricity, but to somehow store it. [NCERT] The writing appears on the paper. Question 10. Does lemon juice or vinegar conduct electricity? Prepare a list of objects around you that are electroplated. Good Conductors of Electricity: The materials which allow the current to pass through them are known as good conductors. Solving the Chemical Effects of Electric Current Multiple Choice Questions of Class 8 Science Chapter 14 MCQ can be of extreme help as you will be aware of all the concepts. (b), Question 3. 7. Clean their metal caps with sand paper. Answer: If the electric potential is negative in the direction of electric current and the Note down the terminal of the battery with which this electrode is connected. Flow of Electrons in the Matter. Spell. (Remember to wash and wipe the ends of tester after testing each liquid). In fact, the average amount of electricity used by people who are not running air conditioning is about 10 kWh a day. Explain the process of electroplating of copper. If they are, then replace the bulb with another bulb. Wrap an electric wire a few times around the tray. Zinc coatings prevent the corrosion of steel articles. Solution: 14.2). 14.3). Hydroxyl ions (OH )move towards the anode and oxygen is collected on it. may be the current is so weak that it does not heat the filament of the bulb allowing it to glow. Refining of metal are for obtaining pure metal. Explain. Many powerplants around the globe produce this resource for the massive consumption now experienced but often at great cost to the environment. Electrolytes conduct current at a slow rate than metals. (i) The wires in the circuit may be loosely connected. Explain why they do this. Connect the negative terminal of battery to the metal sheet. Match. Which one of the following is a weak electrolyte ? The passage of an electric current through a solution causes ……………….. effects. 14.5. may cause the magnetic needle to deflect. Answer: If the tester is working, it can be used to test the materials, i.e., whether it is a conductor or non-conductor of electricity. Question 12. What precautions should be observed when doing electroplating ? These MCQ Questions on Chemical Effects of Electric Current Class 8 with answers pave for a quick revision of the Chapter thereby helping you to enhance subject knowledge. The compass needle will show deflection with tap water, lemon juice and sodium chloride solution. The bulb in the tester does not glow when current is passed through it. (i) liquid A is a better conductor than liquid B. But when salt is dissolved in pure water, it conducts electricity. Answer: (7) Electric iron, mixer and grinder, microwave oven, electric geyser, electric kettle, washing machine, radio set, television set, stereo system computer all work because there is electricity. To her surprise, she found that the compass needle showed deflection. You may also get distilled water from a medical store or a doctor or a nurse). No, it is not advisable for electrician to carry out electrical repairs during heavy downpour because water is a good conductor of electricity and the person can get shock. Take care that the ends are not more than 1 cm apart but at the same time do not touch each other. (d) sides of the container Powdered coal is burnt at high temperature which further turns water into steam. Question 8. 8. 14.4). Compact Fluorescent Lamps. We can test the presence of the small current by using a LED instead of the bulb. The decomposition of an electrolyte when electricity is passed through it, is called Our bodies use electricity to communicate including telling our heart to keep beating. (c) Dilute sulphuric acid Answer: Leave the other end free. So she collected some rainwater in a clean glass tumbler and tested it using a tester. Electricity is a form of energy produced by charges. What is electroplating? (d) photodiode (a) Aluminium Hence, water is avoided in extinguishing electric fires. Take out carbon rods carefully from two discarded cells. From the other plate, an equal amount of copper gets dissolved in the solution. (b), Question 6. Humans cannot survive without it. Solution: Use the tester to test whether distilled water conducts electricity or not. (ii) liquid B is a better conductor than liquid A. (d) Potassium Question 9. For example: All metals including metal wires, copper wires, aluminium foil, etc. Now dissolve a pinch of common salt in distilled water. (a) Sea water Question 3. Does distilled water conduct electricity? Question 6. He finds that the compass needle deflects more in the case of seawater. Question 6. Does pure water conduct electricity? What are insulators ? When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Domestic Use; Generating Electricity. Answer: Why the iron cans are electroplated with tin ? In this activity the bulb glows which shows that lemon juice and vinegar both conducts electricity, hence they are good conductors of electricity. . Explain why these deposits occur. Answer: dtoiakramer PLUS. The bulb does not glow because distilled water is an insulator, since it does not have dissolved salts. Other uses include paint sprayers, air filters and dust removal. Question 5. Objects that are electroplated are door handles, taps, rims of cycles, showers, the handlebar of cycles and bikes, gas burner, tin cans, metallic almirahs, buckles of belts, etc. What is the difference between current flowing through metals and current flowing through liquids ? Question 8. Give some uses of LED. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ……….. terminal of the battery. These Class 8 trucks stand out, not only for their appealing exteriors but for the latest computer technology, keeping them steps ahead of other manufacturers’ trucks. The electrode, connected to the positive terminal of a battery, is called 14.6. We prefer not to do electroplating on iron used for bridges because it is very costly. Take two pieces of copper wire and iron wire. Fill in the blanks. (d) The process of depositing a layer of any desired metal on another material by means of electricity is called _______ Answer: Vinegar, lemon juice and tap water. The disposal of the used conducting solution after electroplating is hazardous and can cause environmental pollution. (a) anode You would conclude that. Answer: STUDY. Use plating artificial jewellery with gold. and ………….. Answer: The bulb does not glow in the set-up shown in figure. 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. Question 4. (a) anode If the current in the circuit is small, how can we test its presence ? Or, the bulb is fused? Every molecule possesses kinetic energy and the sum of K.E is heat energy. (c) semi-conductor (b) Oxalic acid Answer: NCERT Solutions for Class 6, 7, 8, 9, 10, 11 and 12. Electric eels use electricity to ward off enemies. Answer: Question 14. Answer: LED is Light Emitting Diode. Electricity Uses. Answer: How can he do it ? The free copper, being positively charged, gets drawn to the negative terminal of the battery and gets deposited on it. (a) Most liquids that conduct electricity are solutions of ______ , ______ and ______ How would you classify lemon juice or vinegar—a good conductor or a poor conductor? (b) pole This document is highly rated by Class 8 students and has been viewed 50236 times. Activity 6 (NCERT Textbook, Page 176) What results do you obtain? Which properties of chromium make it useful for electroplating on iron ? Paheli had heard that rainwater is as good as distilled water. Answer: Chromium has a good shine, it resists scratches and is corrosion resistant. Take a filter paper soaked in potassium iodide solution to which a pinch of starch is added. Place them in fresh lemon fruit. Answer: Apart from chemical effect, which other effect electric current produce ? How are bridges and automobiles prevented from rusting ? Question 13. In this page, we are providing Electricity Class 10 Extra Questions and Answers Science Chapter 12 pdf download. In case of a fire, before the firemen uses the water hoses, they shut off the main electrical supply for the area. Dec 27, 2020 - Important Questions - Chemical Effects of Electric Current, Science, Class 8 | EduRev Notes is made by best teachers of Class 8. The most extensive use of gold plating is on jewellery and watch cases. Answer: Question 11. If not, what can we do to make it conducting ? Chemical Effects of Electric Current - Class 8 : Notes. The compass needle should show deflection. Artificial jewellery is plated with silver or gold. (c) Sodium chloride Question 10. (iv) conducting properties of liquid cannot be compared in this manner. We will need copper sulphate and two copper plates of size around 10 cm x 4 cm. 3.00. b) An electric iron of resistance 20Ωtakes a current of … Write its one use. Explain. To her surprise she found that the compass needle showed deflection. The loss of copper from solution is cqmpensated and the process goes on. (b) cathode Again test. Answer: Current electricity is when an electrical charge is given a path to move through. Answer: [NCERT] Add a few drops of dilute sulphuric acid to copper sulphate solution to make it more conducting. Can you explain the reason ? Now test if the tester is working or not. Fun facts about the Uses of Electricity. Liquid A is a better conductor than liquid B. Answer: On the other hand the loss of copper from the solution is regained from the impure copper rod which is attached to the positive terminal of the battery. Materials which allow electric current to flow through them are called conductors. Question 11. Question 14. It is concluded that when electric current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate. Add a few drops of lemon juice or dilute hydrochloric acid to distilled water in one cap. LED is a device in which the two terminals inside the glass bulb are connected together with a metallic point of Galluim Arsenide. Answer: It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. Answer: Question 2. Is it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Electric eels use electricity to ward off enemies. (b) coating Answer: Why are LEDs more useful for testing the flow of electric current ? Bridges and automobiles are prevented from rusting by plating them with zinc. Jake three clean plastic or rubber caps of bottles. Which electrode should be attached to the positive terminal of the battery and why? Examples are copper, aluminium, etc. LEDs require very little energy and glow even if a small current is passing through the circuit. Activity 5 (NCERT Textbook, Page 176) If the ends of the wire of tester are touched for a long time, what will happen ? In containers, water evaporates slowly. Hydrogen and Oxygen. Write. A child staying in a coastal region test the drinking water and also the seawater with his tester. Thus food, stored in iron cans, is prevented from being spoilt due to iron by electroplating it by tin. Oxygen bubbles are formed on the electrode connected to the positive terminal of the battery and hydrogen bubbles are formed on the other electrode. When electric current is passed in water hydrogen ions (H+) move towards cathode and get collected over it. By volume of hydrogen gas is twice the volume of oxygen gas. Question 7. We call these two rods electrodes. (ii) The bulb may be fused. What could be the reasons? Electricity was first used in homes for lighting. Solution: Do you find a coating over it? (b), Question 5. The water used in the water hoses is not pure water and is a good conductor of electricity. Answer: Why ? Question 4. the concentration of electricity; can be positive or negative. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. He finds that the compass needle deflects more in the case of seawater. Example 1• An electric rice cooker operates at 240 V and uses a current of 8 A. Thus water which is free of salts are poor conductors while water with salts is a good conductor of electricity. LEDs emitting white light can be used instead of bulbs. Question 10. (b), Question 8. What is the disadvantage of electroplating done in the factories ? Question 20. (8) Electric trains runs with electricity. Question 8. 25% of the city of San Francisco's energy is generated by wind power. Most liquids that conduct electricity are solutions of …………, ………. Question 1. (a) Copper Protection of the surface of bases metals which corrode for e.g., iron is plated with chromium. Electrical charge. If it is still not working then replace the cells with fresh cells. Question 12. There are specific disposal guidelines for environmental protection. Decoration of articles by giving them a layer for e.g., silver plating on cutlery. But the bulb does not glow. (b) Alcohol Terms in this set (11) Electricity. What are electrodes ? (b) chemical Insulators : distilled water, milk. (c) chemical energy into electrical energy Tesla won and AC is delivered to most homes still today. Question 3. Today, the modern sources of entertainment starting from listening music from MP3 players,watching Television, playing movies in DVDs or VCDs or VCRs runs on electricity. Which out of the following does not conduct electricity ? Question 2. Activity 2 (NCERT Textbook, Page 773) Now remove the electrodes from the solution and look at them carefully. (d) electroplating. Question 1. Have you ever imagined how electricity is produced and what's the science behind it? Changes of colour of solutions may occur depending on what solution and electrodes are used. Connect the copper plates to the terminals of a battery and immerse them in copper sulphate solution (Fig. Make sure that the metal caps of the carbon rods are outside the water. Solution: Wait for 3-4 minutes. Answer: It cannot be said for sure that liquid does not conduct electricity because : Question 2. Question 1. We should not do the experiments on electricity by using electric supply from the mains because there is large amount of current and the person using it can get electrocuted. (b) Iron Name one non-metal which a good conductor of electricity. Metal caps of bottles in extinguishing electric fires this process is known as chemical of! It glows may occur depending on what solution and look at them carefully metal sheet a shock of 500! 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Is about 10 kWh a day in containers uses for storing water for liquid B strong magnetic.... The positive terminal of the household for the electrician to carry out electrical outdoors. He finds that the compass needle showed deflection is working or not metals and flowing. Have any salts dissolved in it 11 and 12 and sulphate ions take out the ends of tester! Produced by charges it resists scratches and is a better conductor of electricity through two liquids which! His tester you that are electroplated if you pass current through a solution causes ……………….. Effects working replace. And also the seawater with his tester, honey transferred to the terminal. Separate out and deposit on it ) Refrigerator of rating 400 W for ten hours day... For bridges because it is very costly metal gets dissolved in it as compared to the copper... Electroplating is hazardous and can cause electrocution, as water is a strong used... 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