Here we have an example of long-distance power transmission, showing the value of using high voltages. The generator at left generates 120 V, and a step-up transformer converts it to about 113 kilovolts. This greatly reduces the current, and thereby the resistance losses, over the transmission wires (represented by the 500 ohm resistors). A step-down transformer brings the voltage down to about 114 V for the load at right. The graph on the lower left shows the power transmitted to the load.
For comparison, the same setup without transformers is shown at the bottom. The resistance losses are much higher, and the transmitted power (shown at the lower right) is much lower. (Although the power delivered by the source is much lower as well; but if you compare the power delivered the source to the power consumed by the load, the circuit on top is far more efficient than the circuit on the bottom.)
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