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Ideal transformer

In an ideal transformer no energy is lost. The power in then equals the power out. If you step the voltage up, the current goes down correspondingly, and the other way round.

U_1 I_1 = U_2 I_2

power in equals power out

S = U\,I

apparent power

Symbols

$S$	apparent power	VA
$U$	voltage	V
$I$	current	A

Example

230 V in, 12 V out and 5 A on the secondary side:

$I_1 = 12\cdot 5/230 \approx 0.26$ A.

The side with the highest voltage has the least current, so it can use thinner wire.

Practise the transformer for free →

← Turns ratio · Losses and efficiency →

Part of Electric Power and Machines: The transformer.