A coil has resistance 30 Ω and inductive reactance 20 Ω at 50 Hz. If connected to a 200 V, 100 Hz AC source, what is the current in the coil?
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A coil has resistance 30 Ω and inductive reactance 20 Ω at 50 Hz. If connected to a 200 V, 100 Hz AC source, what is the current in the coil?

G1 Physics · Accepted Answer

Step 1: Inductive reactance depends linearly on frequency: X(L) = 2πfL. Step 2: Initially X(L) = 20 Ω at 100 Hz. At 200 Hz, X(L)′ = 40 Ω. Step 3: The coil resistance remains R = 30 Ω, so new impedance Z = √(R² + X(L)′²). Step 4: Z = √(30² + 40²) = 50 Ω, and I = V/Z = 200/50 = 4.0 A. Final answer: (A) 4.0 A.