ϕ=B⋅S
ϕ=π4×10−3(1−100t)⋅πR2
ϕ=4×10−3×(1)2(1−100t)
ϵ=dt−dϕ
ϵ=dt−d(4×10−3(1−100t))
ϵ=4×10−3(1001)=4×10−5V
When B=0
1−100t=0
t=100sec
Heat =Rϵ2t
Heat =2×10−6(4×10−5)2×100J
Heat =2×10−616×10−10×100J
Heat =0.08J
Heat =80mJ
JEE Main 2021 — Physics Electromagnetism
A circular conducting coil of radius 1m is being heated by the change of magnetic field B passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2μΩ. The magnetic field is slowly switched off such that its magnitude changes in time as
B=π4×10−3T(1−100t)
The energy dissipated by the coil before the magnetic field is switched off completely is E=______\mathrm{mJ}.
Held on 25 Jul 2021 · Verified 6 Jul 2026.
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