Chemical Effects of Electric Current Class 8 Extra Questions and Answers Free PDF Download
Very Short Answer Questions
1. Which one of the following is a good conductor of electricity?
A. copper
B. wood
C. distilled water
D. none of these
Ans. A. Copper is a good conductor of electricity.
2. Electric current produces ______________field.
chemical
B. magnetic
C. physical
D. complex
Ans. B. Magnetic field is produced by Electric current
3. The path through which an electric current flows is called ___________.
A.electric path
B. electric relay
C. short circuit
D. electric circuit
Ans. D. Electric circuit is the path through which an electric current flows.
4. What is the full form of LED?
A. Light Emitting Diode
B. Light Electricity Device
C. Large Emitting Device
D. Large Electricity Diode
Ans. A. Light Emitting Diode is a device which converts electrical energy into light energy.
5. If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the __________terminal of the battery.
A. Positive
B. Negative
C. Both
D. None of these
Ans. B. Negative terminal of the battery attracts Copper ions and hence copper will get deposited on the plate
6. Give any two examples of good conductors of electricity.
Ans. All metals (example gold, copper, iron, etc.) are good conductors of electricity.
7. Give any two examples of insulators.
Ans. Examples of insulators are rubber, wood, plastic, etc.
8. Give examples of any two electrolytes.
Ans. Examples of two electrolytes are copper sulphate and sodium chloride.
9. Name any two metals used for electroplating.
Ans. Gold, silver, chromium are the metals used for electroplating.
Short Answer Question
10. Define electroplating.
Ans. Electroplating is the process of depositing a layer of any desired metal on another material using electricity.
11. Write one use of electroplating.
Ans. Electroplating is mostly used in industry to coat metal products with a thin layer of a different metal that has greater value.
12. Why rubber and plastics do not conduct electricity?
Ans. Because they do not enable electric current to pass through them, rubber and plastics do not conduct electricity. Plastics and rubber act as insulators.
13. Write a short note on electrical testers.
Ans. An electrical tester is a piece of electronic test equipment that is used to identify whether or not there is an electric voltage present in the device being tested. It can also be used to see if a liquid enables electric current to pass through it.
14. Why is it right to say poor conductors instead of bad conductors?
Ans. Because most materials can conduct electricity under certain conditions, it is more accurate to refer to them as poor conductors rather than lousy conductors or insulators.
15. Describe the functioning of a LED.
Ans. LED stands for light-emitting diode, and it is used to detect weak current in a circuit. A LED has two wires linked to it, one of which is slightly longer than the other. The longer lead is always connected to the positive terminal of the battery, while the shorter lead is always connected to the negative terminal.
16. Tap water is considered as a good conductor. Why?
Ans. Since tap water is not pure, it does include many mineral salts that are naturally dissolved in it, making it a good conductor.
17. Distilled water is a poor conductor of electricity. Justify.
Ans. The purest type of water is distilled water. There are no salts or dissolved contaminants in it. As a result, it is a poor electrical conductor.
18. What is the purpose of one long and another shorter lead of a LED?
Ans. The objective of having one long and one shorter LED lead is to ensure that the longer lead is constantly connected to the positive terminal of the battery and the shorter lead is always linked to the negative terminal.
19. If a small amount of sugar is added to distilled water, the resulting solution will be a good conductor or poor conductor of electricity? Explain why.
Ans. Sugar, as a non-electrolyte material, does not create ions when dissolved in water, making it a poor conductor. A sugar solution comprises sucrose molecules but no ions. A sugar aqueous solution is a non-electricity conductor fluid because it lacks ions.
20. Define electromagnetic induction.
Ans. The induced current flowing through the coil in a circuit is always in opposition to the magnet's motion. Electromagnetic induction is the process of producing induced current as a result of a changing magnetic field.
21. State the properties of chromium.
Ans. Chromium has the following characteristics:
a. It is lustrous;
b. It is non-corrosive; and
c. It is scratch resistant.
22. It is advisable to cut the electric supply before putting water over a fire caused due to electricity. Why?
Ans. If not distilled, water is an excellent conductor of electricity. If poured on a fire generated by electricity, it may exacerbate the situation, resulting in accidents. As a result, before putting water on a fire caused by electricity, it is a good idea to turn off the power.
Long Answer Questions
23. With an experiment explain the process of electroplating.
Ans. Copper sulphate and two copper plates (about 10 cm x 4 cm) are required. In a clean and dry beaker, pour 250 mL of distilled water. Two teaspoons of copper sulphate should be dissolved in it. To make the copper sulphate solution more conductible, add a few drops of dilute sulphuric acid. Using sandpaper, clean copper plates. After that, give them a good rinsing and let them air dry. Immerse the copper plates in a copper sulphate solution after connecting them to the terminals of a battery. Allow 15 minutes for the current to pass. Now take the electrodes out of the solution and examine them closely. Copper sulphate dissociates into copper and sulphate when an electric current is applied through the solution. The free copper is attracted to the electrode linked to the battery's negative terminal and deposited there.
Electroplating
Important Questions Class 8 Science Chapter 11
Class 8 Science Chapter 11 Extra Questions
The class 8 science chapter 11 extra questions will help students to answer every question from the chapter with a detailed understanding. The important questions class 8 science chapter 11 Pdf provided here is useful for students in learning every concept of chapter 11 precisely. Chapter 11 of class 8 science deals with the chemical effects of electric current. The chemical effects of the electric current is an important concept we study in class 8 science. This chapter will bring an introduction to the concept of electricity with relevant examples and many detailed experiments. The class 8 science chapter 11 important questions are more reliable content, and with the help of the class 8 science chapter, 11 extra questions students will be able to ace their exams with the desired score.
The important questions class 8 science chapter 11 Pdf provided here comprises of all the questions that will help students to elevate their score with detailed solutions. The important questions for class 8 science chapter 11 study material are made particularly to help students and guide them in a correct way of studying with interesting question banks along with the class 8 science chapter 11 extra questions. Before we start with the practice of class 8 science chapter 11 extra questions let us have a brief revision regarding this chapter.
The chapter begins with the introduction to the concept of electricity in the context of physics. Students are familiar with the term current, in this 21st century, we are completely dependent on electricity. Our lives will be completely disturbed without electricity. In this chapter, students will understand what is current, how the effects of current are being observed. Students will also learn what do we mean by the conduction of electricity. We also learn about what are conductors, how do we classify them depending on the strength of their conducting property.
In this chapter, students will get to know the pros and cons of electricity. Why we should not touch any electrical equipment with wet hands. While explaining why we should not touch electricity with wet hands we come across a simple experiment that is more evidently explaining that water or any liquid is a good conductor of electricity. Students are advised to follow safety instructions and perform these experiments in the presence of the guides.
Later on, the chapter moves forward with the chemical effects of electric current. In this section of the chapter, students will be learning about chemical effects with the help of different solutions. Students will be capable of distinguishing between the conducting and non-conducting solution by performing certain experiments. Students will learn by passing a current through the given solution and conclude the given experiment. The entire chapter will be with many physical experiments and students are advised to perform them with a lot of safety precautions.
Chapter 11 of class 8 physics will make students understand the concept of electric current in detail with suitable examples and physical experiments. By the end of the chapter, students will be able to answer every question regarding the concept of current. Students are advised to focus on the experiments as they will be most frequently asked in the examinations. Students should start studying with quality study materials such as the important questions class 8 science chapter 11 Pdf.
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FAQs on CBSE Important Questions for Class 8 Science Chemical Effects of Electric Current - 2025-26
1. What are conductors and insulators? As per the 2025-26 CBSE pattern, provide two examples for each to secure full marks in a short-answer question.
For a 2-mark question, the answer should be precise. Conductors are materials that allow electric current to pass through them easily. Examples include metals like copper and iron. Insulators are materials that do not allow electric current to pass through them. Examples include rubber and plastic.
2. List four important applications of electroplating that are frequently asked in Class 8 exams.
Four key applications of electroplating are:
Corrosion Prevention: Iron objects, like car parts and bathroom fittings, are coated with chromium or zinc to prevent rusting.
Jewellery: Less expensive metals are coated with a thin layer of gold or silver to make affordable, attractive jewellery.
Food Storage: Tin cans used for storing food are made by electroplating tin onto iron. Tin is less reactive than iron, protecting the food from spoiling.
Strengthening Objects: A layer of a stronger metal can be electroplated onto a weaker one to improve its durability and appearance.
3. Explain the process of electroplating an iron spoon with copper. What are the essential components (anode, cathode, electrolyte) for this setup?
To electroplate an iron spoon with copper, a specific setup is required. The essential components are:
Anode (Positive Electrode): A plate of pure copper.
Cathode (Negative Electrode): The iron spoon to be plated.
Electrolyte: A solution of a copper salt, such as copper sulphate (CuSO₄) dissolved in water.
When an electric current is passed through the copper sulphate solution, the solution dissociates into copper ions (Cu²⁺) and sulphate ions (SO₄²⁻). The positive copper ions are attracted to the negatively charged iron spoon (cathode) and get deposited on it as a thin layer of pure copper. Simultaneously, an equal amount of copper from the copper plate (anode) dissolves into the solution to replenish the copper ions lost, ensuring the process continues.
4. What are the three main chemical effects that can be observed when electric current passes through a conducting liquid?
The three primary chemical effects observed when an electric current passes through a conducting solution (like acidified water or a salt solution) are:
Formation of Gas Bubbles: Bubbles of gas may form on the electrodes. For example, during the electrolysis of water, hydrogen and oxygen gas bubbles are produced.
Deposition of Metal: Metal from the solution can get deposited on the negative electrode (cathode), as seen in the process of electroplating.
Change in Colour of the Solution: The chemical reactions can cause the colour of the electrolyte to change, indicating that a new substance has been formed.
5. Why is pure or distilled water considered a poor conductor of electricity, while tap water conducts it effectively? This is a common HOTS question.
The ability of a liquid to conduct electricity depends on the presence of free-moving charged particles called ions. Distilled water is extremely pure and contains very few ions, making it a poor conductor. Tap water, on the other hand, contains dissolved salts and minerals from its source. These substances dissociate into positive and negative ions, which are free to move and carry electric current through the water, making it a conductor.
6. For a class activity, why is an LED often a better choice than a standard torch bulb in a conductivity tester, especially for testing weak electrolytes like lemon juice?
An LED (Light Emitting Diode) is a better choice than a standard torch bulb for a few key reasons:
High Sensitivity: An LED can light up even when a very weak electric current passes through it. Many substances, like lemon juice or vinegar, are weak conductors and only allow a small current to flow.
Low Power Requirement: A standard bulb requires a significant current to heat its filament until it glows. The weak current from a poor electrolyte is often insufficient to make the bulb glow, leading to the incorrect conclusion that the liquid is a non-conductor. An LED avoids this issue.
7. To prevent rusting, iron objects are coated with zinc in a process called galvanisation. Why is a more reactive metal like zinc preferred over a less reactive one like tin for this purpose?
Zinc is preferred over tin for protecting iron due to a principle called sacrificial protection. Zinc is more reactive than iron. If the zinc coating on a galvanised object gets scratched, the exposed zinc will corrode (react with air and water) in preference to the iron. The zinc sacrifices itself to protect the iron. In contrast, if a tin coating is scratched, the exposed iron (being more reactive than tin) will start to rust rapidly at the scratch point.
8. What is meant by the electrolysis of water? Identify the gases produced at the positive and negative electrodes during this important chemical process.
Electrolysis of water is the process of using electricity to decompose water (H₂O) into its constituent elements, which are hydrogen and oxygen. A small amount of acid is usually added to the water to make it conductive.
During this process:
At the negative electrode (cathode), hydrogen gas (H₂) is produced.
At the positive electrode (anode), oxygen gas (O₂) is produced.
