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An LC circuit with inductance L = 0.1 H and capacitance C = 10⁻³ F lies in a plane. The loop area is 1 m² and is placed in a magnetic field perpendicular to its plane. Starting at t = 0, the field increases linearly as B = B0 + (beta)t with beta = 0.04 T/s. Find the maximum magnitude of the current in the circuit (in mA).

1. 0.4 mA
2. 4 mA
3. 40 mA
4. 0.04 mA

Correct answer: 4 mA

Solution

A constant EMF e = A*(dB/dt) = A*beta acts on the series LC loop. The charge oscillates about the value Ce. The maximum current in undamped LC oscillation driven by a step EMF is I_max = e*sqrt(C/L).

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