Electrical Energy Generation, Transmission and Utilization
What this domain tests
This domain covers how electricity is generated, why it is transmitted at high voltage, how it is distributed, and how it is used in heating, lighting and drives. Numerical questions often compare line losses or compute energy charges.
Core rules
- Generation sources include thermal, hydro, nuclear, solar photovoltaic, wind and biomass; each has different capital cost, operating cost and availability.
- Transmission at high voltage reduces current for the same power, so I²R line loss falls sharply. Voltage is stepped up and down by transformers.
- Distribution uses lower voltages for safety and insulation economy; three-phase four-wire systems supply mixed single-phase and three-phase loads.
- Utilization includes resistive heating, lighting, welding, and motors. Efficiency = useful output/input; tariff charges usually apply per kWh plus fixed charges.
Worked example
A feeder of 2 Ω carries 50 A. Line loss = I²R = 2500 × 2 = 5000 W. If the same power is sent at double the voltage, the current halves to 25 A and the loss becomes 625 × 2 = 1250 W, one quarter of the original. This is the core reason transmission voltages are high, despite the increased insulation requirements.
Traps that cost marks
Confusing power (kW) with energy (kWh); thinking high transmission voltage reduces the power delivered; ignoring transformer losses when comparing schemes; and calculating line loss with the total load current when several feeders share it.