Practice question

**Transformer principle** alternating current in primary creates changing flux linking secondary, emf induced e = -N dΦ/dt, flux same through both, so V∝N. For N_p=550, N_s=1100, V_p=110 V rms, V_s= V_p×N_s/N_p=220 V, step-up factor 2, efficiency <100% due to copper, iron, hysteresis losses. Beyond the resonant frequency, the inductive reactance ( X_L = ω L ) increases with frequency, while the capacitive reactance ( X_C = (1/ω C) ) decreases. Since X_L grows faster than X_C decreases, the net reactance ( X_L - X_C ) becomes positive, increasing the impedance ( Z = √(R² + (X_L - X_C)²) ). Applying X_L = ωL, X_C =