A transformer with turns ratio $\frac{{\mathrm{N}}_1}{{\mathrm{N}}_2}=\frac{50}{1}$ is connected to a 120 V AC supply. If primary and secondary circuit resistances are 1.5 kW and 1Wrespectively, then find out power of output. 

Given, turn ratio of a transformer,

$$\begin{gathered} \frac{{\mathrm{N}}_1}{{\mathrm{N}}_2}=\frac{50}{1} \\ \Rightarrow {\mathrm{N}}_1 =50{\mathrm{N}}_2 \\ \mathrm{Since}, \frac{{\mathrm{N}}_1}{{\mathrm{N}}_2}=\frac{{\mathrm{V}}_1}{{\mathrm{V}}_2} \\ 50=\frac{120}{{\mathrm{V}}_2} \left[{\mathrm{V}}_1=120 \mathrm{V} \left(\mathrm{given}\right)\right] \\ \Rightarrow {\mathrm{V}}_2=\frac{12}{5}\mathrm{V} \\ \mathrm{Output} \mathrm{power} \mathrm{at} \mathrm{secondary} \mathrm{coil}, \\ {\mathrm{P}}_{\mathrm{S}}=\frac{{\mathrm{V}}_2^2}{{\mathrm{R}}_2} \left[{\mathrm{R}}_2=1\mathrm{\Omega } \left(\mathrm{given}\right)\right] \\ =\frac{{\left({\displaystyle \frac{12}{5}}\right)}^2}{1}=\frac{144}{25}=5.76 \mathrm{W} \end{gathered}$$

Given, turn ratio of a transformer,