Skip to content
Login Register

#eddy currents

5 public questions tagged with this topic.

Mutual Induction and Mutual Inductance

A magnet is dropped through a vertical copper tube. The magnet’s fall is slower than expected due to what effect?

**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. The falling magnet induces currents in the copper tube, which create a magnetic field opposing the magnet’s motion, slowing its fall. This is an application of Lenz’s law. 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,

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

View Details
Induced EMF Due to Change in Magnetic Field

A metal ring is placed near a solenoid. When an AC current flows through the solenoid, the ring experiences a force. Thi

**Uniform field change** in coil produces emf proportional to area and turns, for circular coil radius 0.16 m area πr²=0.0804 m², B 0.12 T deformed to wire in 0.6 s, ΔΦ=0.12×0.0804=0.00965 Wb, e=0.00965/0.6=0.0161 V, illustrating area change also induces emf. The AC current creates a varying magnetic field, inducing currents in the ring that generate an opposing field, leading to a repulsive or attractive force based on Lenz’s law. 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

Ref: NCERT > Physics Book > Electromagnetic Induction > Induced EMF Due to Change in Magnetic Field

View Details
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

View Details
Transformer, AC Generator and LC Oscillations

What is the primary energy loss mechanism in a real transformer that reduces its efficiency?

**AC generator** converts mechanical to electrical, emf e = N B A ω sin ωt, maximum e₀ = N B A ω, frequency = rotation frequency, transformer cannot work on DC because steady flux no induction, LC oscillations energy swaps between ½ L I² and ½ Q²/C at ω₀=1/√(LC). In a real transformer, energy losses occur due to resistance in the windings ( I² R losses), flux leakage, eddy currents, and hysteresis. Among these, resistance in the windings (copper loss) is a primary mechanism, converting electrical energy into heat. Applying X_L = ωL, X_C = 1/ωC, Z = √(R² + (X_L - X_C)²), I_rms =

Ref: NCERT > Physics Book > Alternating Currents > Transformer, AC Generator and LC Oscillations

View Details