Worked example: A 220 V, 1000 W electric heater runs for 30 minutes. (a) Find its resistance and current. (b) Compute the energy consumed in kWh and the cost at ₹8 per kWh. (c) Why do transmission lines use high voltage? Step 1: P = V²/R → R = V²/P = 48400/1000 = 48.4 Ω. I = P/V = 1000/220 ≈ 4.55 A. Step 2: Energy = 1 kW × 0.5 h = 0.5 kWh = 1.8 × 10⁶ J. Cost = 0.5 × 8 = ₹4. Step 3: Transmitting 1000 W at 220 V needs 4.55 A, losing I²R in the lines; at 220 kV the current is 1000× smaller (4.55 mA) and I²R losses are a million times smaller — that is the entire economic argument for high-voltage grids, plus thinner (cheaper) conductors.