NCERT Solutions for Class 10 Science Chapter 12 – Magnetic Effects of Electric Current
Chapter 12 of Class 10 Science is where Physics starts to feel like magic — but of course, it's not magic at all. It's the science of electromagnetism, one of the four fundamental forces of nature. This chapter explains how a simple wire carrying current can create a magnetic field around it, how that principle powers every electric motor on the planet, and how the reverse — moving a wire through a magnetic field — generates electricity in every power station. These are not just textbook ideas; they are the reason your phone charges, your fan spins, and your city gets electricity.
The NCERT Solutions for Class 10 Science for this chapter go beyond just giving answers — they explain the direction of forces using Fleming's rules, describe Faraday's groundbreaking discoveries, and help students visualise what happens inside a generator or transformer. Students preparing for CBSE board exams should pay special attention to the diagram-based questions and rule application problems, both of which are consistently asked. Myclass24 provides detailed, student-friendly solutions for every question in this chapter.
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Chapter 12 Deep Dive – Concepts, Rules & Solved Exercise Breakdown
This chapter covers magnetic fields produced by straight wires, circular loops, and solenoids; the force on current-carrying conductors; Fleming's Left Hand Rule for motors; electromagnetic induction; Fleming's Right Hand Rule for generators; and AC vs DC comparison. Below are structured tables to help you revise quickly — especially useful before board exams and unit tests.
Magnetic Field Sources in Chapter 12
| Source | Field Pattern | Key Property |
|---|---|---|
| Straight current-carrying wire | Concentric circles around wire | Field strength ∝ current; ∝ 1/distance |
| Circular loop | Field resembles bar magnet at centre | More turns = stronger field |
| Solenoid (coil) | Uniform field inside; like a bar magnet | One end N-pole, other S-pole |
| Electromagnet | Controlled magnetic field | Field strength controlled by current |
Fleming's Rules – Quick Reference
| Rule | Used For | Fingers Represent |
|---|---|---|
| Fleming's Left Hand Rule | Electric Motor (force on conductor) | Forefinger = B field; Middle = current; Thumb = Force/Motion |
| Fleming's Right Hand Rule | Electric Generator (induced current) | Forefinger = B field; Middle = induced current; Thumb = Motion |
| Right Hand Thumb Rule | Direction of field around a wire | Thumb = current direction; Fingers curl = field direction |
Electric Motor vs Electric Generator
| Feature | Electric Motor | Electric Generator |
|---|---|---|
| Principle | Magnetic force on current-carrying conductor | Electromagnetic induction |
| Energy conversion | Electrical → Mechanical | Mechanical → Electrical |
| Key Rule | Fleming's Left Hand Rule | Fleming's Right Hand Rule |
| Current type output | Uses input current (AC or DC) | AC generator or DC generator |
| Real-world example | Fan, mixer, washing machine | Power station turbine, bicycle dynamo |
AC vs DC – Key Differences
| Property | AC (Alternating Current) | DC (Direct Current) |
|---|---|---|
| Direction | Changes direction periodically | Flows in one direction only |
| Frequency (India) | 50 Hz | Zero (no frequency) |
| Source | AC generator, power stations | Battery, solar cell |
| Transmission | Can be stepped up/down (transformer) | Cannot use transformer |
| Home supply (India) | 220 V, 50 Hz | Not used for mains supply |
Important NCERT Questions to Focus On
| Question | Topic | Why It Matters |
|---|---|---|
| In-text Q1 | Magnetic field direction around wire | Tests Right Hand Thumb Rule |
| In-text Q3 | Solenoid field pattern | Common diagram question |
| Exercise Q4 | Working of electric motor | Frequently asked 5-mark question |
| Exercise Q8 | Electromagnetic induction | Tests Faraday's experiment understanding |
| Exercise Q11 | Domestic electric circuits & safety | Real-world application, 3-mark question |
Chapter 12 rewards students who understand the "why" behind each rule. Knowing that a motor works because a magnetic force acts on a current-carrying conductor — and being able to derive the direction of that force using Fleming's Left Hand Rule — is far more useful than memorising definitions alone. Myclass24 explains each concept visually and step-by-step so that even complex topics like electromagnetic induction become straightforward.
FAQs for NCERT Solutions Class 10 Science Chapter 12 Magnetic Effects Current
The close relationship between electricity and magnetism was discovered by Hans Christian Oersted in 1820. He found that a current-carrying conductor produces a magnetic field around it. When current flows through a straight wire, magnetic field lines form concentric circles around the wire. The direction of the magnetic field is given by the Right-Hand Thumb Rule: if you hold the wire in your right hand with the thumb pointing in the direction of current flow, the curled fingers indicate the direction of the magnetic field. The strength of the field depends on the magnitude of current and the distance from the wire. When the wire is bent into a coil (solenoid), the magnetic fields from each turn add up, creating a strong, uniform field inside the coil similar to a bar magnet — with a north pole at one end and a south pole at the other.
Fleming's Left-Hand Rule is used to find the direction of force on a current-carrying conductor placed in a magnetic field. Stretch the thumb, index finger, and middle finger of the left hand mutually perpendicular to each other. The index finger points in the direction of the magnetic field (B), the middle finger in the direction of current (I), and the thumb gives the direction of the force (thrust) on the conductor. This force is the basis of an electric motor. An electric motor converts electrical energy into mechanical energy. It consists of a rectangular coil placed in a magnetic field. When current passes through the coil, different sides experience force in opposite directions (by Fleming's Left-Hand Rule), causing the coil to rotate. A split ring commutator ensures the current reverses every half rotation, maintaining continuous rotation. Motors are used in fans, pumps, refrigerators, and electric vehicles.
Household electrical circuits have several safety devices to prevent damage and hazards. A fuse is a thin wire of low melting point alloy (tin-lead or aluminium) connected in series in a circuit. If current exceeds the safe limit (due to short circuit or overloading), the fuse wire melts and breaks the circuit. Modern installations use Miniature Circuit Breakers (MCBs) instead, which automatically trip when excess current flows and can be reset. An earthing wire connects the metallic body of appliances to the ground, so if a live wire accidentally touches the body, current flows safely to earth instead of through a person. The three-pin plug system uses live (red), neutral (black), and earth (green) wires. These safety measures prevent electric shock, fire hazards, and damage to expensive appliances, making electrical safety a critical concern in every home.
Both AC and DC generators convert mechanical energy into electrical energy through electromagnetic induction, but the type of current they produce differs. In an AC generator (alternator), the coil rotates in a magnetic field and is connected to an external circuit via slip rings (continuous rings). As the coil rotates, the direction of induced current reverses every half rotation, producing alternating current (AC). Household electricity supply is AC. In a DC generator, slip rings are replaced by a split ring commutator, which reverses the connection to the external circuit every half rotation. This ensures current always flows in the same direction in the external circuit, producing direct current (DC). Batteries and solar cells also produce DC. AC is preferred for long-distance power transmission because it can be easily stepped up or down using transformers.
Electromagnetic induction is the process of generating an electric current in a conductor by changing the magnetic field around it. This was discovered by Michael Faraday in 1831. When a magnet is moved in and out of a coil, or when the current in a nearby coil changes, the changing magnetic flux induces an electromotive force (EMF) and hence a current in the coil. The direction of induced current is given by Fleming's Right-Hand Rule or Lenz's Law (the induced current always opposes the change causing it). The magnitude of induced EMF depends on the rate of change of magnetic flux, the number of turns in the coil, and the strength of the magnetic field. Electromagnetic induction is the operating principle of generators, transformers, and many other electrical devices, making it one of the most important concepts in modern physics.