# Secondary voltage referred to the primary

I am studying transformers and I am not completely understanding a basic detail, but it is annoying me.

When we draw the equivalent circuit of a transformer, why is the secondary voltage referred to the primary written as $V_{2}'=\frac{N_1}{N_2}V_2$ ?

• What do V2 and V'2 represent? – Bruce Abbott Mar 18 '17 at 16:49
• $V_2$ is the voltage on secondary and $V_{2}'$ is the voltage $V_2$ referred to the primary. – Vinícius Lopes Simões Mar 18 '17 at 16:54