An offshoot of Joules’ Law is that when transmitting electrical power, the current is kept as low as possible in order to reduce energy losses associated with heat of the electrical cables. Because the power being transferred is the product of the voltage and the current, we can still get the same power transferred if we halve the current and double the voltage, or; make the current very, very small and make the voltage very, very big.
So power -lines transmit power at a voltage of up to 400,000 volts. Then, as the power gets closer to the home, the voltage is reduced in stages, and correspondingly the current gets increased. This occurs in appiances called transformers.
I came across a lovely interactive explanation of this when in honeymoon in Hong Kong.
I couldn’t resist.