--- title: "NCERT Solutions Class 8 Science Electricity: Magnetic and Heating Effects" url: https://www.swavid.com/science/class/8/chapter/electricity-magnetic-and-heating-effects/ncert-solutions dateModified: 2026-10-07T16:12:49+00:00 --- # NCERT Solutions Class 8 Science Electricity: Magnetic and Heating Effects This chapter's questions cover concepts related to the magnetic and heating effects of electric current, electromagnets, and how electric cells and batteries generate electricity. Free PDF (6 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-8/swavid-ncert-solutions-class-8-science-chapter-4-electricity-magnetic-and-heating-effects-81283d95cf.pdf ## Keep the curiosity alive ### Question 1 *1 mark · Fill in the blank* Fill in the blanks: (i) The solution used in a Voltaic cell is called ________. (ii) A current carrying coil behaves like a _______ . **Part (i)** 1. A Voltaic cell contains two electrodes dipped in a liquid called an electrolyte. Answer (i): electrolyte **Part (ii)** 1. A current carrying coil produces a magnetic field and behaves like an electromagnet. Answer (ii): electromagnet > Common mistake: Confusing electrolyte with electrode or writing general terms instead of the specific textbook terms. ### Question 2 *1 mark · True or false* Choose the correct option: (i) Dry cells are less portable compared to Voltaic cells. (ii) A coil becomes an electromagnet only when electric current flows through it. (iii) An electromagnet, using a single cell, attracts more iron paper clips than the same electromagnet with a battery of 2 cells. - True/False - True/False - True/False **Part (i)** 1. Voltaic cells use liquid electrolytes in open containers, making them less portable and inconvenient for everyday use compared to sealed dry cells. Answer (i): False **Part (ii)** 1. A coil exhibits magnetic properties only when electric current flows through it; the magnetic effect disappears when current stops. Answer (ii): True **Part (iii)** 1. A battery with more cells provides a larger current, creating a stronger magnetic field that attracts more paper clips than a single cell. Answer (iii): False > Common mistake: Assuming that a single cell produces a stronger magnetic field than a battery with more cells. ### Question 3 *1 mark · MCQ* An electric current flows through a nichrome wire for a short time. (i) The wire becomes warm. (ii) A magnetic compass placed below the wire is deflected. Choose the correct option: - Only (i) is correct - Only (ii) is correct - Both (i) and (ii) are correct - Both (i) and (ii) are not correct **Solution** 1. When an electric current flows through a nichrome wire, it encounters resistance and gets warm due to the heating effect of electric current. 2. The current-carrying wire also produces a magnetic field around it, causing a nearby magnetic compass to deflect. 3. Therefore, both statements (i) and (ii) are correct. **Answer:** (c) Both (i) and (ii) are correct > Common mistake: Forgetting that electric current has both magnetic and heating effects simultaneously. ### Question 4 *2 marks · Very short answer* Match the items in Column A with those in Column B. Column A: (i) Voltaic cell (ii) Electric iron (iii) Nichrome wire (iv) Electromagnet. Column B: (a) Best suited for electric heater (b) Works on magnetic effect of electric current (c) Works on heating effect of electric current (d) Generates electricity by chemical reactions **Solution** 1. Match each item in Column A to its correct description in Column B based on textbook principles. 2. (i) Voltaic cell matches with generates electricity by chemical reactions. 3. (ii) Electric iron matches with works on heating effect of electric current. 4. (iii) Nichrome wire matches with best suited for electric heater. 5. (iv) Electromagnet matches with works on magnetic effect of electric current. **Answer:** (i)-(d), (ii)-(c), (iii)-(a), (iv)-(b) > Common mistake: Incorrectly pairing the nichrome wire with general electrical conduction instead of its heating application. ### Question 5 *1 mark · MCQ* Nichrome wire is commonly used in electrical heating devices because it (i) is a good conductor of electricity. (ii) generates more heat for a given current. (iii) is cheaper than copper. (iv) is an insulator of electricity. **Solution** 1. Nichrome wire offers higher resistance to the flow of electric current compared to copper wire. 2. Higher resistance causes more electrical energy to be converted into heat energy for a given current. 3. Therefore, option (ii) is correct. **Answer:** (b) generates more heat for a given current. > Common mistake: Choosing option (i) because all metals conduct electricity, failing to realize why nichrome is specifically chosen over copper. ### Question 6 *3 marks · Short answer* Electric heating devices (like an electric heater or a stove) are often considered more convenient than traditional heating methods (like burning firewood or charcoal). Give reason(s) to support this statement considering societal impact. **Solution** 1. Electric heating devices like heaters and stoves do not produce smoke or harmful gases inside living spaces, unlike firewood or charcoal. 2. They can be turned on and off instantly using a switch, providing better control and safety. 3. They reduce indoor air pollution, protect health, and prevent the felling of trees for firewood. **Answer:** Electric heating devices are cleaner, safer, provide instant control, and reduce indoor air pollution compared to burning firewood or charcoal. > Common mistake: Focusing only on electricity cost instead of discussing health, environmental, and societal benefits. ### Question 7 *3 marks · Short answer* Look at the Fig. 4.4a. If the compass placed near the coil deflects: (i) Draw an arrow on the diagram to show the path of the electric current. (ii) Explain why the compass needle moves when current flows. (iii) Predict what would happen to the deflection if you reverse the battery terminals. **Part (i)** 1. Draw an arrow on the connecting wires of Fig. 4.4a pointing from the positive terminal to the negative terminal of the cell. Answer (i): Arrow pointing from the positive terminal to the negative terminal. **Part (ii)** 1. When electric current flows through the coil, it produces a magnetic field around it. 2. The compass needle is a tiny magnet which experiences a magnetic force in this magnetic field and deflects. Answer (ii): The electric current produces a magnetic field that exerts a force on the compass needle, causing it to move. **Part (iii)** 1. Reversing the battery terminals reverses the direction of the electric current flowing through the coil. 2. This reverses the magnetic poles of the electromagnet, causing the compass needle to deflect in the opposite direction. Answer (iii): The direction of deflection of the compass needle will be reversed. **Answer:** (i) Arrow drawn from positive to negative terminal of the cell. (ii) Electric current produces a magnetic field around the coil, which exerts a force on the tiny magnet of the compass needle. (iii) Reversing the battery terminals reverses the direction of the electric current and thus reverses the magnetic poles (polarity) of the electromagnet, which reverses the direction of deflection of the compass needle. > Common mistake: Forgetting that reversing the current reverses the poles of the electromagnet. ### Question 8 *3 marks · Short answer* Suppose Sumana forgets to move the switch of her lifting electromagnet model to OFF position (in introduction story). After some time, the iron nail no longer picks up the iron paper clips, but the wire wrapped around the iron nail is still warm. Why did the lifting electromagnet stop lifting the clips? Give possible reasons. **Solution** 1. When the switch is left ON, electric current continuously flows through the wire wrapped around the iron nail. 2. Due to the heating effect of electric current, the electrical energy is converted into heat, making the wire warm. 3. Over time, the chemicals in the cell get completely used up, making the cell 'dead' so it can no longer supply electricity to run the electromagnet. **Answer:** The lifting electromagnet stopped lifting because the continuous flow of current drained the cell completely, making it dead, while the current flowing through the wire produced heat due to the heating effect of electric current. > Common mistake: Thinking the iron nail itself demagnetized permanently instead of recognizing that the cell ran out of power. ### Question 9 *1 mark · MCQ* In Fig. 4.12, in which case the LED will glow when the switch is closed? **Solution** 1. Lemon juice contains acids and salts, which make it a conducting solution (electrolyte) that allows electric current to flow through the circuit. 2. Pure water is a poor conductor of electricity, so the circuit remains incomplete in case (b). 3. Therefore, the LED will glow only in case (a) where lemon juice is used. **Answer:** (a) Only in circuit (a) > Common mistake: Assuming pure water conducts electricity just like tap water. ### Question 10 *3 marks · Short answer* Neha keeps the coil exactly the same as in Activity 4.4 but slides the iron nail out, leaving only the coiled wire. Will the coil still deflect the compass? If yes, will the deflection be more or less than before? **Solution** 1. Yes, the coil will still deflect the compass because a current-carrying coil of wire behaves as an electromagnet even without an iron core. 2. However, the deflection will be less than before. 3. Inserting an iron nail inside the core of the coil makes the electromagnet much stronger, so removing the iron nail weakens the magnetic field and reduces the deflection. **Answer:** Yes, the coil will still deflect the compass, but the deflection will be less than before because the iron core makes the electromagnet stronger. > Common mistake: Thinking that a coil without an iron nail has no magnetic field at all. ### Question 11 *1 mark · MCQ* We have four coils, of similar shape and size, made up from iron, copper, aluminium, and nichrome as shown in Fig. 4.13. When current is passed through the coils, compass needles placed near the coils will show deflection. - Only in circuit (a) - Only in circuits (a) and (b) - Only in circuits (a), (b), and (c) - In all four circuits **Solution** 1. When an electric current passes through any conductor shaped as a coil, it produces a magnetic field around it due to the magnetic effect of electric current. 2. Iron, copper, aluminium, and nichrome are all conductors of electricity, although they offer different levels of resistance. 3. Since current flows through all four closed circuits containing these conducting coils, all of them will show a magnetic effect and deflect the compass needles. **Answer:** (iv) In all four circuits > Common mistake: Thinking that only copper or specific metals can produce a magnetic field when carrying current. ## Frequently asked questions ### How many questions are there in the NCERT solutions for Class 8 Science Chapter 4? This chapter contains a total of 11 questions covering various types such as fill in the blanks, multiple choice, short answer, true or false, and very short answer. You can find step-by-step solutions for all of them in SwaVid's free PDF available on this page only. ### Which major topics are covered in the exercise questions of this chapter? The questions cover important concepts like the conduction of electricity through liquids, heating and magnetic effects of electric current, and the properties of dry cells and electromagnets. They also explore specific topics such as nichrome wire resistance, drained batteries, and electromagnet poles. ### Which type of question is considered the hardest in this chapter and how should I approach it? Numerical or application-based questions on the heating effect and resistance of nichrome wire or coils of different conducting materials can be challenging. To approach these, first revise the core principles thoroughly and then practice the detailed explanations provided in SwaVid's free PDF on this page. ### How should I write my answers to score full marks in Class 8 Science exams? To secure full marks, structure your answers clearly by defining key scientific terms, explaining the underlying cause such as the magnetic or heating effect of current, and drawing neat diagrams where required. Following the structured formats in SwaVid's step-by-step solutions on this page will help you write precise answers. ### Is the free PDF for this chapter available for the 2026-27 session? Yes, the complete chapter solutions aligned with the new NCERT book for the 2026-27 session are ready for you. You can access and download SwaVid's free PDF and detailed step-by-step solutions directly on this page. ## Related pages - [Class 8 Science chapters](https://www.swavid.com/science/class/8) Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student