What is Electricity Effects Exercises in Class 8 Science NCERT?

The Class 8 Science NCERT Chapter 4 — Electricity: Magnetic and Heating Effects exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, electricity questions, magnetic effect questions, competency-based questions. It includes multiple-choice questi…

What does the NCERT Class 8 Science Electricity: Magnetic and Heating Effects exercise section cover?

The Class 8 Science NCERT Chapter 4 u2014 Electricity: Magnetic and Heating Effects exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, electricity questions, magnetic effect questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Electricity: Magnetic and Heating Effects exercises?

Class 8 students should approach the Electricity: Magnetic and Heating Effects exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and electricity questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Electricity: Magnetic and Heating Effects questions competency-based as per NEP 2020?

Yes, the Electricity: Magnetic and Heating Effects exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 4 exercises?

The Chapter 4 u2014 Electricity: Magnetic and Heating Effects exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, electricity questions, magnetic effect questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Electricity: Magnetic and Heating Effects exercise set present two statements u2014 an Assertion (A) and a Reason (R) u2014 and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Electricity: Magnetic and Heating Effects exercises is to read through all theory parts of NCERT Curiosity Chapter 4 once, write down the key terms such as NCERT exercises, electricity questions, magnetic effect questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions u2014 first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

What does the NCERT Class 8 Science Electricity: Magnetic and Heating Effects exercise section cover?

The Class 8 Science NCERT Chapter 4 — Electricity: Magnetic and Heating Effects exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, electricity questions, magnetic effect questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the Electricity: Magnetic and Heating Effects exercises?

Class 8 students should approach the Electricity: Magnetic and Heating Effects exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and electricity questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these Electricity: Magnetic and Heating Effects questions competency-based as per NEP 2020?

Yes, the Electricity: Magnetic and Heating Effects exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 4 exercises?

The Chapter 4 — Electricity: Magnetic and Heating Effects exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, electricity questions, magnetic effect questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science Electricity: Magnetic and Heating Effects exercise set present two statements — an Assertion (A) and a Reason (R) — and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting Electricity: Magnetic and Heating Effects exercises is to read through all theory parts of NCERT Curiosity Chapter 4 once, write down the key terms such as NCERT exercises, electricity questions, magnetic effect questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions — first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

TOPIC 14 OF 50

Electricity Effects — Exercises

🎓 Class 8 Science CBSE Theory Ch 4 — Materials: Metals and Non-Metals ⏱ ~21 min

🌐 Language: [gtranslate]

🧠 AI-Powered MCQ Assessment ▲

This MCQ module is based on: Electricity Effects — Exercises

No. of Questions:

Difficulty Level:

Myaischool Lt Science Assessment ▲

[myaischool_lt_science_assessment grade_level="class_8" science_domain="chemistry" difficulty="basic"]

Chapter Summary

Chapter 4 explored how an ordinary electric current can do three amazing things at the same time — create magnetism, generate heat, and drive chemical reactions. Here's the big picture.

1. Magnetic Effect (Oersted, 1820)

Every current-carrying wire creates a magnetic field around it. A compass near the wire deflects when current flows.

2. Electromagnet

Coil of insulated wire wound on a soft iron core. Switch ON → strong magnet; switch OFF → not a magnet. Strength depends on turns, current, and core.

3. Uses of Electromagnets

Lifting cranes in scrap yards, electric bells, loudspeakers, telephone earpieces, MRI machines, maglev trains, and electric motors.

4. Heating Effect

A wire's resistance turns electrical energy into heat. Nichrome glows red-hot; copper stays cool.

5. Filament Bulb

Tungsten filament (m.p. 3400 °C) in inert gas glows brightly at 2500 °C.

6. Heating Devices

Iron, heater, toaster, geyser, kettle, hair dryer — all use nichrome coils.

7. Safety — Fuse & MCB

Fuse (tin-lead) melts on overload; MCB trips automatically. Never use copper wire as fuse.

8. Chemical Effect

Current through electrolytes causes chemical changes. Distilled water and sugar solution do not conduct.

9. Cells

Primary (throw-away) vs secondary (rechargeable). Chemical ⇄ electrical energy.

10. E-waste

Old cells have toxic metals. Always dispose via e-waste channels — never in regular bins.

Keywords

ElectromagnetTemporary magnet made by current in coiled wire around a soft iron core.

Magnetic fieldRegion around a magnet/current where its effect can be felt.

Oersted's experimentCompass near a current-carrying wire deflects.

ArmatureThe moving iron piece (with hammer) inside an electric bell.

ResistanceOpposition offered to the flow of current.

NichromeNi-Cr-Fe alloy used for heating coils; high resistance, high m.p.

TungstenMetal with very high m.p. (~3400 °C) used in bulb filaments.

FuseSafety device; thin tin-lead wire that melts on overload.

MCBMiniature Circuit Breaker — trips to cut off excess current.

ElectrolyteSolution that contains free ions and conducts electricity.

ElectrolysisChemical decomposition by passing current through an electrolyte.

ElectroplatingCoating one metal with another using electrolysis.

Primary cellSingle-use cell; chemical reaction not reversible.

Secondary cellRechargeable cell; reaction can be reversed.

E-wasteElectronic waste including old batteries; toxic if dumped.

NCERT-Style Exercises

Which of the following figures represents an electromagnet?

Answer: (B). An electromagnet is made by wrapping an insulated coil of wire around an iron core (nail) and connecting it to a cell. Options (A) and (C) are permanent magnets.

Oersted noticed that a compass needle placed near a current-carrying wire gets deflected. What important conclusion did this observation lead to?

Solution: The deflection proved that an electric current produces a magnetic field around itself. In other words, electricity and magnetism are related phenomena. This discovery (1820) gave birth to the science of electromagnetism and led to the invention of electromagnets, electric motors and generators.

Why is tungsten used as the filament material in an incandescent bulb?

Solution: Tungsten is used because (i) it has a very high melting point (~3400 °C), so it does not melt even when the filament glows white-hot at 2500 °C; (ii) it can be drawn into very thin wires and coiled to provide high resistance in a small space, which produces bright light. An inert gas (argon) is filled inside the bulb to prevent the hot tungsten from burning in oxygen.

Why is nichrome used in heating appliances (heater, iron, toaster) instead of copper?

Solution: Nichrome has (i) much higher resistance than copper, so the same current produces a lot of heat in nichrome — perfect for heating; (ii) a high melting point (~1400 °C), so it can glow red-hot without melting; (iii) it does not oxidise/rust easily, giving long life. Copper has very low resistance and would barely warm up, and in house wiring we actually want this so the wires do not heat.

Can an iron nail be magnetised by passing current through a coil wound around it? Explain.

Solution: Yes. When current flows through the coil, a magnetic field is produced, and the iron nail inside the coil gets magnetised. The nail becomes a strong magnet as long as current flows and can pick up pins. The moment current is switched off, the field collapses and the nail loses its magnetism (because soft iron is magnetised only temporarily). This is exactly what an electromagnet is.

How does an electric bell work? Draw a labelled diagram.

Solution: When the bell-push is pressed, current flows through the coil making it an electromagnet. The electromagnet pulls the iron armature; the hammer attached to the armature strikes the gong producing a ring. As the armature moves, the contact screw is separated → circuit breaks → electromagnet stops → spring pulls the armature back → circuit reconnects → electromagnet pulls again. This rapid make-and-break action happens many times per second, giving continuous ringing.

What is an electric fuse? Why is it important in household wiring?

Solution: A fuse is a short piece of thin wire made of tin-lead alloy having a low melting point, connected in series with an appliance or the main circuit. If the current exceeds a safe value (due to overload or a short circuit), the fuse wire melts and breaks the circuit. This prevents (i) damage to expensive appliances, (ii) overheating of house wiring, and (iii) electrical fires. Without a fuse (or MCB), any fault would allow large currents to flow unchecked — a serious safety hazard.

Suppose Sumana forgets to switch off her lifting electromagnet at the scrap yard. After some time, she notices it can no longer pick up heavy iron nails. Give three possible reasons why.

Solution — 3 reasons:

Battery drained: Continuous current has used up the chemicals in the cells. Low current → weak magnetic field → less lifting power.
Coil overheated: Long current flow heats the coil; hot copper has higher resistance, so less current flows for the same voltage and the magnet weakens.
Insulation damage / short-circuit in the coil: Heat can damage the thin insulation on the wire, causing some turns to short-circuit. Fewer effective turns means a weaker field.

Lesson: always switch off the electromagnet when not lifting — saves power and extends equipment life.

In the setup shown below (Fig 4.11), in which case will the LED glow when the switch is closed — when the electrodes are dipped in lemon juice, or in pure water?

Answer: The LED glows only when the electrodes are dipped in lemon juice. Lemon juice contains citric acid that dissociates into positive and negative ions — these free ions carry the current, completing the circuit. Pure (distilled) water has almost no ions; it is a non-conductor, so no current flows and the LED stays OFF.

Q10

Neha keeps the coil exactly the same as in Activity 4.4 but slides the iron nail out, leaving only the coiled wire connected to the cell. Will the coil still deflect a nearby compass? If yes, will the deflection be more or less than before?

Answer: Yes, the coil will still deflect a nearby compass, because current flowing through any coil produces a magnetic field around it. However, the deflection will be less than before. Earlier, the iron nail acted as a core that concentrated and strengthened the magnetic field. With the nail removed, the field exists only in air (much weaker), so the compass needle deflects only by a small angle.

Q11

We have four identical coils of wire wrapped around cores made of different materials — iron, copper, aluminium, nichrome (Fig 4.12). Same current flows through each. Which one will act as the strongest electromagnet?

Answer: The coil with the IRON core will act as the strongest electromagnet. Reason: Iron is a ferromagnetic material — it gets strongly and easily magnetised when placed in a magnetic field, because its internal tiny magnetic regions line up quickly. Copper, aluminium, and nichrome are non-magnetic (or only extremely weakly magnetic) — they do not boost the field much beyond what the bare coil would produce. That is why every practical electromagnet uses a soft iron core.

AI Tutor

Science Class 8 — Curiosity

Ready

Hi! 👋 I'm Gaura, your AI Tutor for Electricity Effects — Exercises. Take your time studying the lesson — whenever you have a doubt, just ask me! I'm here to help.