A thermal power plant produces electric power of 600 KW at 4000 V, which is to be transported to a place 20 km away from the power plant for consumers' usage . It can be transported either directly with a cable of large current carrying capacity or by using a combination of step-up and step-down transformers at the two ends. The drawback of the direct transmission is the large energy dissipation . In the method using transformers , the dissipation is much smaller. In this method, a step-up transformer is used at the plant side so that the current is reduced to a smaller value. At the consumers' end , a step-down transformer is used to supply power to the consumers at the specified lower voltage . It is reasonabler to assume that the power cable is purely resistive and the transformers are ideal with a power factor unity. All the currents and voltages mentioned are rms values.
If the direct transmission method with a cable of resistance $0.4\Omega k{m}^{-}$ is used, the power dissipation (in %) during transmission is

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