im having a hard time understanding current and power. i want to connect a step-up transformer directly to the mains. the uk mains is 240 Volts and the sockets are rated at 13 Amps.

Now my transformer would be marked something like: output is 1,000 Volts and outputs 20mA. <- is that all my circuit will be able to draw, or is that how much the transformer can take before over heating?

Appliances like kettles and tvs have makings on them that say how much power they take... But how do i find out how much power my circuit will take.

I know the power equation things but how do i use them to find how much my circuit will want to draw?

Does my circuit, connected to the secondary of the transformer affect how much the primary coil will take?

how much can the primary take, etc...

Can someone please help me understand this?

thanks!