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#induction

21 public questions tagged with this topic.

Lenz's Law, Eddy Currents and Applications

A circular coil of radius 10 cm and 220 turns rotates at 60 rad/s in a 0.02 T field. What is the maximum emf induced?

**Eddy currents** are circulating currents induced in bulk conductor by changing flux, oppose motion, cause damping, heating, energy loss, minimized by laminating core into thin sheets insulated, increasing resistance, reducing eddy current magnitude, used in induction heating and braking. A = π r² = 3.14 × (0.1)² = 0.0314 m² . ε₀ = N B A ω = 220 × 0.02 × 0.0314 × 60 = 8.2992 V ≈ 8.3 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt) and U

Ref: NCERT > Physics Book > Electromagnetic Induction > Lenz's Law, Eddy Currents and Applications

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Self-Induction and Self-Inductance

A coil of self-inductance 1.2 H has its current increased from 2 A to 6 A in 0.4 s. What is the magnitude of the induced

**Energy stored in inductor** U =½ L I², L inductance, I current, energy in magnetic field, density u = B²/(2μ₀), B=μ₀ n I inside solenoid, U = (B²/2μ₀)×volume, illustrating equivalence of circuit and field energy. ε = L (Δ I/Δ t) . Δ I = 6 - 2 = 4 A , Δ t = 0.4 s . ε = 1.2 × (4/0.4) = 1.2 × 10 = 12 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt) and U =

Ref: NCERT > Physics Book > Electromagnetic Induction > Self-Induction and Self-Inductance

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Self-Induction and Self-Inductance

A wheel with 6 spokes of 0.6 m each rotates at 45 rpm in a 0.5 T field. What is the induced emf?

**Self-inductance of solenoid** L = μ₀ N² A / l, N total turns, A cross-section, l length, for N=650 turns per meter means n=650 m⁻¹, if length 1 m N=650, A=0.014, L=4π×10⁻⁷×650²×0.014/1=0.00743 H, self-induced emf magnitude L |dI/dt|, dI/dt=12 A/s, e=0.089 V, opposes change. ω = 2π × (45/60) = 1.5π rad/s . ε = (1/2) B ω R² = (1/2) × 0.5 × 1.5π × (0.6)² = 0.8478 V ≈ 0.85 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt)

Ref: NCERT > Physics Book > Electromagnetic Induction > Self-Induction and Self-Inductance

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AC Generator, Back EMF and Time Duration of EMF

A loop of 0.3 m × 0.12 m moves out of a 0.4 T field at 2 m/s along its longer side. How long does the emf last?

**AC generator** emf e = N B A ω sin ωt, maximum when coil plane parallel to field, zero when perpendicular, time duration of emf when loop moves out of field t = L/v, L side along motion, v speed, e = B l v while cutting. For loop 0.28×0.14 m B=0.3 T v=1.4 m/s along longer side 0.28 m, cutting side 0.14 m, e=0.3×0.14×1.4=0.0588 V, duration t=0.28/1.4=0.2 s, emf exists only during exit. Time = distance/velocity, distance = width along motion = 0.12 m. t = (0.12/2) = 0.06 s . Using Φ = B A cosθ, e = -N dΦ/dt = -N A

Ref: NCERT > Physics Book > Electromagnetic Induction > AC Generator, Back EMF and Time Duration of EMF

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AC Generator, Back EMF and Time Duration of EMF

A rod rotates at 25 rad/s in a 0.3 T field. If the length from the axis to the tip is 0.8 m, what is the emf induced?

**Back emf** in motor opposes applied voltage, e_b = N B A ω sin ωt, reduces net current, at start ω=0 e_b=0 current large, as speed increases e_b increases limiting current, power conversion mechanical, principle of motor and generator reciprocity. ε = (1/2) B ω R² . ε = (1/2) × 0.3 × 25 × (0.8)² = 2.4 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt) and U = ½ L I², result 2.4 V follows, reflecting Faraday's law and Lenz's opposition.

Ref: NCERT > Physics Book > Electromagnetic Induction > AC Generator, Back EMF and Time Duration of EMF

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Mutual Induction and Mutual Inductance

A solenoid of 600 turns and length 0.8 m induces an emf of 2 V in a nearby coil when its current changes from 1 A to 4 A

**Mutual inductance calculation** M = e₂/(dI₁/dt), for 200 turns length 0.5 m nearby coil e=0.5 V dI=2 A dt=0.2 s dI/dt=10 A/s, M=0.5/10=0.05 H, depends on geometry, orientation, number of turns, area, separation, coupling coefficient k = M/√(L₁ L₂) ≤1. ε = M (Δ I/Δ t) . Δ I = 4 - 1 = 3 A , Δ t = 0.2 s . M = (ε/(Δ I/Δ t)) = (2/(3/0.2)) = (2/15) = 0.133 H ≈ 0.13 H . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L =

Ref: NCERT > Physics Book > Electromagnetic Induction > Mutual Induction and Mutual Inductance

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Motional EMF - Rod and Rectangular Loop

A rectangular loop of 0.26 m × 0.42 m moves out of a 0.45 T field at 0.7 m/s along its shorter side. What is the emf?

**Loop sides 35 cm and 15 cm** moving out B=0.8 T v=1.5 m/s perpendicular to shorter side 15 cm, so cutting side =35 cm=0.35 m? Actually motion perpendicular to shorter side means longer side cuts, e= B×(long side)×v =0.8×0.35×1.5=0.42 V, illustrating motional emf e = B L v. ε = B l v , l = 0.42 m . ε = 0.45 × 0.42 × 0.7 = 0.1323 V ≈ 0.132 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt) and

Ref: NCERT > Physics Book > Electromagnetic Induction > Motional EMF - Rod and Rectangular Loop

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Magnetic Flux and Faraday's Laws of Induction

A coil of 120 turns experiences a magnetic flux change from 0 to 0.04 Wb in 0.08 s. What is the induced emf?

**Faraday's first law** emf induced when flux linking coil changes, second law magnitude proportional to rate of change, e = -dΦ/dt, for N turns e = -N dΦ/dt, flux Φ = B A cosθ, change can be due to B change, A change, or θ change, all produce emf. ε = N (Δ Φ/Δ t) . Δ Φ = 0.04 Wb , Δ t = 0.08 s , N = 120 . ε = 120 × (0.04/0.08) = 120 × 0.5 = 60 V . Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N

Ref: NCERT > Physics Book > Electromagnetic Induction > Magnetic Flux and Faraday's Laws of Induction

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Magnetic Flux and Faraday's Laws of Induction

A metal plate swings like a pendulum through a magnetic field. The slowing of its motion is primarily due to what?

**Faraday's first law** emf induced when flux linking coil changes, second law magnitude proportional to rate of change, e = -dΦ/dt, for N turns e = -N dΦ/dt, flux Φ = B A cosθ, change can be due to B change, A change, or θ change, all produce emf. The motion induces currents in the plate, which produce an opposing magnetic field, exerting a force that resists the motion (Lenz’s law), slowing it down. Using Φ = B A cosθ, e = -N dΦ/dt = -N A dB/dt = B l v = N B A ω sinωt, L = μ₀ N²A/l, M = e/(dI/dt)

Ref: NCERT > Physics Book > Electromagnetic Induction > Magnetic Flux and Faraday's Laws of Induction

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PHYSICS

A coil of 40 turns experiences a magnetic flux change from 0 to 0.01 Wb in 0.05 s. What is the induced emf?

Given: A coil of 40 turns experiences a magnetic flux change from 0 to 0.01 Wb in 0.05 s. What is the induced emf? These values define the system as per NCERT data. Formula: varepsilon = N Δ Phi/Δ t. This is standard NCERT relation. Substitution & Calculation: Δ Phi = 0.01 Wb, Δ t = 0.05 s, N = 40 . varepsilon = 40 × 0.01/0.05 = 40 × 0.2 = 8 V . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Relevant Physics topic covering fundamental principles,

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PHYSICS

A coil is wound tightly around a core material. If the current through it changes rapidly, the induced emf opposing this

This is self-induction, where a changing current in a coil induces an emf that opposes the change, proportional to the coil’s self-inductance. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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Induction Morphogen -ll

Which of the following statements best defines 'Induction' in developmental biology?

Induction describes fundamental process where one embryonic tissue, acting as inducer, influences developmental fate of neighboring responding tissue via diffusible or contact-mediated chemical signals. Inducer secretes growth factors such as FGF, BMP antagonists like Noggin, Chordin and Wnt modulators that bind receptors on competent responder, initiating signal transduction cascades like MAPK and Smad that alter gene regulatory networks redirecting differentiation. Classic demonstration is Spemann organizer graft inducing host ectoderm to form neural plate rather than epidermis. Induction ma

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Embryonic Induction and Tissue Interaction.

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