Practice question

**Wattless current** occurs in pure inductor or capacitor, I_rms non-zero but average power zero because φ=±90°, cos φ=0, energy oscillates between source and field, no dissipation, used in choke coil to limit current without heating, unlike resistor where power dissipated. X_C = (1/ω C) = (1/314 × 14 × 10⁻⁶) ≈ 227.5 Ω . Z = √(R² + X_C²) = √(70² + 227.5²) = √(4900 + 51756.25) ≈ 238.2 Ω . Applying X_L = ωL, X_C = 1/ωC, Z = √(R² + (X_L - X_C)²), I_rms = V_rms/Z, P = V_rms I_rms cosφ, V_s/V_p = N_s/N_p, calculation gives 238.2 Ω, consistent with phasor analysis and resonance condition X_L = X_C.