## Reducing Power Losses by Transmitting Electricity at High Voltages

When a currentflowsalong a wire of resistancethepower loss in the the resistor needed to drive the current throughthe resistor is equal toByreducing the current, we reduce the power loss. We can reduce thecurrent by increasing the voltage at the input to the wire.

Suppose the power supply has a power output of 200W. We can adjustthe voltage of the supply to 20 V then

The power burnt in the wire is

You may also have seen the expression for power,Itis important to realise thatinthis expression is the voltage drop along the wire, not the supplyvoltage. The voltage drop along the wire is

Thenasbefore.

Suppose we adjust the voltage of the power supply so that it is 40V then

The power burnt in the wire is

The voltage drop along the wire is

Thenasbefore.

Doubling the supply voltage has halved the current and halved thevoltage across the resistor. Because the power burnt variesasandthepower wasted in the wire is reduced toofit's value.