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Turns ratio

A transformer has two coils around a shared iron core. The alternating current in the primary coil creates a magnetic field that induces a voltage in the secondary coil. The voltage is transformed in the same ratio as the number of turns.

\frac{U_1}{U_2} = \frac{N_1}{N_2}

voltage follows the turns

\frac{I_1}{I_2} = \frac{N_2}{N_1}

current is transformed inversely

Symbols

$U_1,\ U_2$	primary and secondary voltage	V
$N_1,\ N_2$	number of turns
$I_1,\ I_2$	primary and secondary current	A

Example

$N_1 = 1000$ , $N_2 = 50$ and $U_1 = 230$ V:

$U_2 = 230\cdot 50/1000 = 11.5$ V.

A transformer only works with AC. DC gives no changing magnetic field.

Practise the transformer for free →

Ideal transformer →

Part of Electric Power and Machines: The transformer.