Why are high voltage power lines used for transmission? Because it causes less radiation of electric energy

The answer above was marked wrong by VCAA;
The 'correct' answer is 'For a given power, the larger the transmission voltage the smaller the current, 'but I don't think that this is necessarily the REASON, and if so, why is it the case

vcaa physics paper 2004

I studied power for my senior design project in college.

You have three basic equations for power:

1. Power = Voltage x Current

2. Power = Voltage^2 / Resistance

3. Power = Current^2 x Resistance

As you can see from equation one, if you increase voltage, you don't need as much current for a given amount of power.

So what happens is that since the current is low and the resistance of the wire is low, from equation three, you'll have low power losses in the wire in the form of heat (I^2R).

The 'correct' answer is 'For a given power, the larger the transmission voltage the smaller the current.

It is because along the transmission the transmission power loss is directly proportional to the Square of the current. So Current must be remain lowest possible to minimize transmission loss. The only way to do this is to increase voltage level since power is the product of voltage and current. The higher the voltage the lower will be the current.