CBSE Class 8 Science Chapter 4: Electricity: Magnetic and Heating Effects — Assertion & Reason
CBSE Class 8 Science Assertion & Reason
Expert crafted · Instant PDF download · 2026-27
The following Assertion and Reason questions are based on Chapter 4: Electricity: Magnetic and Heating Effects from the NCERT Class 8 Science textbook Curiosity. Each question has four options — read both the Assertion (A) and Reason (R) carefully before selecting your answer.
How to attempt Assertion & Reason questions:
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is NOT the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Assertion & Reason Questions
1
Assertion (A): A magnetic compass needle gets deflected when placed near a wire carrying electric current.
Reason (R): An electric current flowing through a conductor produces a magnetic field around it.
Reason (R): An electric current flowing through a conductor produces a magnetic field around it.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. This phenomenon, discovered by Hans Christian Oersted, is known as the magnetic effect of electric current.
2
Assertion (A): Inserting an iron nail into a current-carrying coil makes it a much stronger electromagnet.
Reason (R): Iron is a magnetic material that increases the strength of the magnetic field when placed inside the coil.
Reason (R): Iron is a magnetic material that increases the strength of the magnetic field when placed inside the coil.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. For practical applications, most electromagnets use an iron core to significantly boost their magnetic strength.
3
Assertion (A): An electromagnet has only one magnetic pole, unlike a permanent bar magnet.
Reason (R): The poles of an electromagnet can be reversed by changing the direction of the electric current.
Reason (R): The poles of an electromagnet can be reversed by changing the direction of the electric current.
Answer: (d)
A is false, but R is true. Just like a permanent magnet, an electromagnet always has two poles (North and South), which can be swapped by reversing the current's direction.
4
Assertion (A): The strength of an electromagnet can be increased by increasing the number of turns in the coil.
Reason (R): A battery with more cells provides a larger current, which also creates a stronger magnetic field.
Reason (R): A battery with more cells provides a larger current, which also creates a stronger magnetic field.
Answer: (b)
Both A and R are true, but R is NOT the correct explanation of A. Both statements are true ways to increase an electromagnet's strength, but the reason does not explain why increasing the number of turns works.
5
Assertion (A): Nichrome wire gets much hotter than a copper wire of the same size when the same current is passed through them.
Reason (R): Nichrome offers higher resistance to the flow of electric current compared to copper.
Reason (R): Nichrome offers higher resistance to the flow of electric current compared to copper.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Higher resistance causes more electrical energy to be converted into heat energy, which is why nichrome is used in heating appliances.
6
Assertion (A): Electric room heaters and electric irons contain a coil of wire called a heating element.
Reason (R): These appliances work on the principle of the magnetic effect of electric current.
Reason (R): These appliances work on the principle of the magnetic effect of electric current.
Answer: (c)
A is true, but R is false. These household appliances work on the heating effect of electric current, not the magnetic effect.
7
Assertion (A): The amount of heat generated in a wire depends on its material, length, and thickness.
Reason (R): The duration for which the current flows has no effect on the heat generated in the wire.
Reason (R): The duration for which the current flows has no effect on the heat generated in the wire.
Answer: (c)
A is true, but R is false. The heat generated depends on the material, thickness, and length of the wire, as well as the duration for which the current flows.
8
Assertion (A): In a Voltaic cell, a chemical reaction between the metal electrodes and the electrolyte produces electricity.
Reason (R): Voltaic cells use two metal plates of the exact same material dipped in a liquid electrolyte.
Reason (R): Voltaic cells use two metal plates of the exact same material dipped in a liquid electrolyte.
Answer: (c)
A is true, but R is false. A Voltaic cell requires two plates made of different materials (e.g., copper and zinc) to function properly and generate electricity.
9
Assertion (A): A simple electric cell can be made using a lemon, a copper wire, and an iron nail.
Reason (R): The lemon juice acts as an electrolyte that helps conduct electricity between the two different metal electrodes.
Reason (R): The lemon juice acts as an electrolyte that helps conduct electricity between the two different metal electrodes.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. The lemon juice provides the acidic medium necessary for the chemical reaction to occur between the copper and iron, generating a small electric current.
10
Assertion (A): A dry cell uses a liquid acid as its electrolyte to generate electricity.
Reason (R): The dry cell consists of a zinc container that acts as the negative terminal.
Reason (R): The dry cell consists of a zinc container that acts as the negative terminal.
Answer: (d)
A is false, but R is true. A dry cell is called "dry" precisely because its electrolyte is a thick moist paste, not a liquid.
11
Assertion (A): Rechargeable batteries like Lithium-ion can be used forever without ever wearing out.
Reason (R): Rechargeable batteries can be charged and reused multiple times to prevent wastage.
Reason (R): Rechargeable batteries can be charged and reused multiple times to prevent wastage.
Answer: (d)
A is false, but R is true. While they can be reused multiple times, rechargeable batteries do not last forever and will slowly wear out after being charged and used many times.
12
Assertion (A): Dead batteries should be safely disposed of in special e-waste recycling facilities.
Reason (R): Batteries contain harmful materials like acids and heavy metals that can damage the environment if thrown in regular garbage.
Reason (R): Batteries contain harmful materials like acids and heavy metals that can damage the environment if thrown in regular garbage.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Proper recycling prevents toxic substances from leaching into the environment and allows valuable materials to be reused.
13
Assertion (A): Alessandro Volta proved that electricity in his experiments came from the frog's leg itself.
Reason (R): Volta used saltwater-soaked paper instead of a frog's leg to generate an electric current.
Reason (R): Volta used saltwater-soaked paper instead of a frog's leg to generate an electric current.
Answer: (d)
A is false, but R is true. Galvani thought the electricity came from the frog. Volta proved him wrong by showing the electricity came from the reaction between the metals and the liquid (saltwater), inventing the first battery.
14
Assertion (A): Lifting electromagnets in cranes use permanent magnets to lift heavy iron objects in scrap yards.
Reason (R): The crane operator can easily control the electromagnet by switching the current ON and OFF.
Reason (R): The crane operator can easily control the electromagnet by switching the current ON and OFF.
Answer: (d)
A is false, but R is true. Cranes use strong electromagnets, not permanent magnets. This allows the operator to drop the heavy items simply by turning off the electric current.
15
Assertion (A): It is important to use appropriate wires, plugs, and sockets rated for the specified electric current in household circuits.
Reason (R): Overheating due to the heating effect of electric current can melt plastic parts and lead to electrical fires.
Reason (R): Overheating due to the heating effect of electric current can melt plastic parts and lead to electrical fires.
Answer: (a)
Both A and R are true, and R is the correct explanation of A. Safety devices and properly rated equipment minimize the risks caused by unwanted heating in electrical transmission.
❓ Frequently Asked Questions
What is covered in CBSE Class 8 Science Chapter 4 Electricity: Magnetic and Heating Effects?
This chapter covers all key topics from Electricity: Magnetic and Heating Effects as per CBSE 2026-27 syllabus.
Is this Assertion & Reason useful for CBSE board exams?
Yes, designed for CBSE Class 8 board exam preparation covering the complete syllabus.
Are these CBSE Class 8 Science Assertion & Reason updated for 2026-27?
Yes, all content at eBookPublisher is updated as per the latest 2026-27 CBSE syllabus.
How many chapters are in CBSE Class 8 Science?
All chapters of CBSE Class 8 Science are covered at eBookPublisher with free Assertion & Reason for each chapter.
Can I study Electricity: Magnetic and Heating Effects online for free?
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