Power transmission:

The most multifaceted, and important, problems is power transmission.

Generators produce the large voltages and currents at the power plant; say from turbines driven by the falling water. The problem: getting electricity from the plant to the businesses, homes, and other facilities which need it. This process involves the use of the long wire transmission lines. Also require transformers to change the voltages to the higher or lower values.

A radio transmitter produces a high frequency ac. The problem: getting power to be radiated by antenna, located some distance from transmitter. This involves the use of a radio frequency transmission line. The most common kind is coaxial cable. Two-wire line is used some times. At ultra high and microwave frequencies,  the other kind of transmission line, called as a waveguide, is often employed. The overriding concern in the power transmission system is minimizing the loss. Power wastage occurs entirely as the heat in line conductors and dielectric, and in the objects near the line. Some loss can take the form of unwanted electromagnetic radiation from the transmission line. In an ideal transmission line, all of power is VA power; that is, it is in form of an ac in the conductors and an alternating voltage between them.

It is undesirable to have the power in a transmission line exist in form of true power. This translates either into heat loss in line, radiation loss, or both of them. The place for true power dissipation is in load, such as electrical appliances or the radio antennas. Any true power in the transmission line represents power which cannot be used by the load, as it doesn't show up there.