A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm s⁻¹. The induced emf in the loop when the radius is 2 cm is

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(4) 3.2π μV. φ=Bπ r², so |ε|=B·2π r(dr)/(dt). |ε|=0.04×2π×(2×10⁻²)×(2×10⁻³). Collecting the numbers: 0.04×2×2×2=0.32, and the powers of ten give 10⁻⁵, so |ε|=3.2π×10⁻⁶ V=3.2π μV.

A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm s⁻¹. The induced emf in the loop when the radius is 2 cm is

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