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Electromagnetic Induction and Alternating Current

NIOS · Class 12 · Physics

Flashcards for Electromagnetic Induction and Alternating Current — NIOS Class 12 Physics. Quick Q&A cards covering key concepts, definitions, and formulas.

45 questions35 flashcards5 concepts

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A labeled diagram illustrating the concept of magnetic flux through a plane area placed in a uniform magnetic field, showing how the angle between the area vector and magnetic field lines affects the
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35 Flashcards
Card 1Faraday's Law

State Faraday's Law of Electromagnetic Induction. Write the formula for a coil with N turns.

Answer

Faraday's Law: The magnitude of the induced emf in a loop is equal to the rate of change of magnetic flux linked with it. For a single loop: |ε| = dΦ_B / dt For a coil with N turns: |ε_total| = N ×

Card 2Lenz's Law

State Lenz's Law. How is it combined with Faraday's Law mathematically?

Answer

Lenz's Law: When a current is induced in a conductor, the direction of the induced current is such that its magnetic effect OPPOSES the change (in flux) that induced it. Combined Faraday-Lenz Law: ε

Card 3Faraday's Law – Numerical

A 75-turn circular coil of radius 35 mm has its axis parallel to a uniform magnetic field. The field changes from 25 mT to 50 mT in 250 ms. Find the induced emf.

Answer

Given: N = 75 turns, R = 35 mm = 0.035 m B₁ = 25 mT = 0.025 T, B₂ = 50 mT = 0.050 T t = 250 ms = 0.250 s Rate of change of field: dB/dt = (B₂ − B₁)/t = (0.050 − 0.025)/0.250 = 0.10 T/s Flux per turn

Card 4Eddy Currents

What are Eddy Currents? Why are they considered undesirable in many devices, and how are they minimised?

Answer

Eddy Currents: When a solid conductor (like a metal sheet or plate) is placed in a changing magnetic field, induced closed loops of current are set up inside the bulk of the conductor. These are calle

Card 5Self-Inductance

Define Self-Inductance. Write the formula relating magnetic flux to self-inductance and the formula for induced back emf.

Answer

Self-Inductance (L): It is the property of a coil by which it opposes any change in the current flowing through it. The magnetic flux linked with the coil is proportional to the current. Formula: Φ =

Card 6Self-Inductance of Solenoid

Derive the formula for the self-inductance of a solenoid of length ℓ, cross-sectional area A, and N turns.

Answer

Step-by-Step Derivation: Step 1 – Magnetic field inside solenoid: Using Ampere's Law: B = μ₀ × n × I where n = N/ℓ (turns per unit length) Step 2 – Total magnetic flux through N turns: Φ = N × B × A

Card 7Self-Inductance – Numerical

A solenoid is 1 m long, 20 cm in diameter, and contains 10,000 turns of wire. A current of 2.5 A is reduced to zero in 1.0 ms. Calculate the magnitude of the back emf.

Answer

Given: ℓ = 1 m, diameter = 20 cm → radius = 0.10 m A = π × (0.10)² = π × 0.01 = 3.14 × 10⁻² m² N = 10,000 turns I₁ = 2.5 A, I₂ = 0 A, t = 1.0 ms = 1.0 × 10⁻³ s Step 1 – Find Self-Inductance: L = μ₀ N

Card 8Mutual Inductance

Define Mutual Inductance. Write the formula for induced emf in the secondary coil due to changing current in the primary coil.

Answer

Mutual Inductance (M): When two coils are placed close to each other, a changing current in coil A (primary) causes a changing flux through coil B (secondary), inducing an emf in B. This property is c

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What are the important topics in Electromagnetic Induction and Alternating Current for NIOS Class 12 Physics?
Key topics in Electromagnetic Induction and Alternating Current include Chapter Overview: Electromagnetic Induction and AC, Electromagnetic Induction and AC — Complete Concept Map, Complete Mind Map of Electromagnetic Induction and AC Chapter. These are the concepts NIOS Class 12 examiners draw on most — study them first, then practise related questions.
How to score full marks in Electromagnetic Induction and Alternating Current — NIOS Class 12 Physics?
Understand the core concepts first, then work through the 45 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.
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There are 35 flashcards for Electromagnetic Induction and Alternating Current covering key definitions, formulas, and concepts. Use them daily for 10–15 minutes for best results.

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