Atoms are very tiny, less than a billionth of a meter in diameter. The wire is “full” of atoms and free electrons and the electrons move among the atoms. Although the electrons are actually moving through the wire slowly, we say that the speed of electricity is near the speed of light (extremely fast).

Mahesh Shenoy

It is because the current in a circuit is equal to Charge x Velocity. The charge of the electrons in a few cm of copper wire is very large. For instance, it is similar to the total charge of a D-cell. In order to convey a current, they have only to move very slowly indeed.

about 1mm per second

Light travels through empty space at 186,000 miles per second. The electricity which flows through the wires in your homes and appliances travels much slower: only about 1/100 th the speed of light.

In conclusion, electricity can travel as far as the energy losses are lower than the total energy travelling through the conductor. If it was long enough, no electricity would be mesured at the end of the conductor, because all energy was turned into heat and irradiated into the air.

The primary reason that power is transmitted at high voltages is to increase efficiency. The higher the voltage, the lower the current. The lower the current, the lower the resistance losses in the conductors. And when resistance losses are low, energy losses are low also.

Electricity flows through water because it contains ions of dissolved salts and metals. Distilled water, which does not contain impurities, does not conduct electricity.

So even though electricity may travel much farther on high-voltage transmission lines – dozens or hundreds of miles – losses are low, around two percent. And though your electricity may travel a few miles or less on low-voltage distribution lines, losses are high, around four percent.