Commercial electricity is generated and transmitted as three-phase electricity. Instead of a single emf, three separate wires carry currents for the emfs ε₁=ε₀ cos ωt, ε₂=ε₀ cos(ωt +120°), and ε₃=ε₀ cos(ωt−120°) over three parallel wires, each of which supplies one-third of the power. This is why the long-distance transmission lines you see in the countryside have three wires. Suppose the transmission lines into a city supply a total of 450 MW of electric power, a realistic value.
b. In fact, transformers are used to step the transmission-line voltage up to 500 kV rms. What is the current in each wire?
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