RBSE Class 12 Physics Chapter 6 — Electromagnetic Induction: Most Repeated Questions (2013–2026)

The magnitude of the electromotive force ( ϵ ) induced in a closed circuit is directly proportional to the rate of change of magnetic flux (Φ_B) linked with the circuit

ϵ=|-NdΦ_B/dt|

All solved questions for this chapter are in the full RBSE Physics PYQ book.

v=rω

dϵ=Bvdr

dϵ=B(rω)dr

The total induced EMF ( ϵ ) between the ends of the rod is found by integrating the EMF of all such elements from r=0 to r=L

ϵ=∫₀^Ldϵ

ϵ=∫₀^LBωrdr

ϵ=Bω∫₀^Lrdr

ϵ=Bω[r²/2]₀^L

ϵ=Bω(L²/2-0²/2); ϵ=1/2BωL²

ϵ=1/2BωL²

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Lenz's Law

The direction of the induced current (or EMF) is such that it opposes the very cause (the change in magnetic flux) that produces it

ϵ=-NdΦ_B/dt

Lenz's law obeys law of conservation of energy because the direction of the induced current creates an opposing magnetic field, ensuring that external work must be done (mechanical energy spent) to change the magnetic flux, and this work is converted into electrical energy

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Let a current I₂ flow through the outer coil. Since r₁≪r₂ , the magnetic field (B₂) produced by the outer coil can be considered uniform over the entire area of the small inner coil. The field at the center of the outer coil is:

B₂=μ₀N₂I₂/2r₂

The magnetic flux (Φ₁) linked with one turn of the inner coil is:

Φ₁=B₂⋅A₁

Φ₁=(μ₀N₂I₂/2r₂)(πr₁²)

The total magnetic flux linkage (Φ₁₂) with the inner coil (with N₁ turns) is:

Φ₁₂=N₁Φ₁=N₁(μ₀N₂I₂/2r₂)(πr₁²)

The mutual inductance M is defined as: Φ₁₂=MI₂

M=Φ₁₂/I₂

M=(N₁(μ₀N₂I₂/2r₂)(πr₁²))/I₂

M=μ₀N₁N₂πr₁²/2r₂

All solved questions for this chapter are in the full RBSE Physics PYQ book.

E=-NdΦ/dt

For the number of turns N=1

|E|=dΦ/dt

|E|=d(BAcosθ)/dt; |E|=d(BA)/dt

A=Lx

|E|=d(BLx)/dt; |E|=BLdx/dt

dx/dt=v

|E|=BLv

All solved questions for this chapter are in the full RBSE Physics PYQ book.