Household electric power in most of Western Europe is supplied at 240 V, rather than the 120 V that is standard in the United States and Canada. What are the advantages and disadvantages of each system?

Voltage is the working agent from the power source of electrical circuit that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating lamp.

Joule’s law of heating states that the amount of generated heat in a conductor carrying current is proportional to the square of the current flow through the circuit when the electrical resistance and current supply is constant.

$$\begin{gathered} P=\frac{V^2}{R}t \\ P=l^{2}Rt \end{gathered}$$

Where P is the heat loss, V is the voltage, R is the resistance, I is the current and t is the time for which current is flowing.

$120V$ is considered to be safer since it is lower voltage. If by any chance, human come in direct contact of power supply then electrical shock so experienced will be less harmful if the power supply is low voltage. So such accidents are not so harmful.

$220V$is cheaper to transmit because it requires small current which can be transmit through thin wires. Thin wires results in high resistance which decreases power loses such as generation of heat in wire.

Therefore, 120V is safe while 220V is cheaper.