Transformer – Summary of formulas

Remember $V_1/V_2=N_1/N_2$

Then it follows:

$V_1\ \I_1=V_2\ \I_2$

and again it follows:

$V_1/V_2=I_2/I_1$

Therefore:

$I_2/I_1=N_1/N_2$

Remember the first formula and all the others follow.