Why does a transformer not work with direct current (DC)?
**Resistor in AC** behaves as DC, no reactance, impedance Z=R, current follows voltage exactly, average power over cycle V_rms I_rms, for 200 V rms, 80 Ω, P=500 W? Actually 200²/80=500 W, peak current √2×2.5=3.535 A, average power ½ V_peak I_peak. A transformer relies on a changing magnetic flux to induce voltage in the secondary coil via mutual induction. DC provides a constant current, producing a steady magnetic field with no flux change, so no voltage is induced. 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 g
Ref: NCERT > Physics Book > Alternating Currents > AC Through Resistor - Phasor and Power