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Problem 6 - Olympiad
A circular loop of radius R is placed in a magnetic field B(t) = B₀ sin ωt. Derive the induced current as a function of time if resistance is R₀.
A. (B₀ωπR²/R₀) cos ωt
B. (B₀πR²/R₀) ω cos ωt
C. (B₀ωR²/R₀) cos ωt
D. (B₀πR²/R₀) sin ωt
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Correct: B
Φ = B*A = B₀ sin ωt * πR². EMF = -dΦ/dt = -B₀ ω πR² cos ωt. I = EMF/R₀ = -(B₀ ω πR²/R₀) cos ωt. Magnitude only considered here.