[tex]U_p=36 kV=36*10^{3} V\\a) n=\frac{N_p}{N_s}=\frac{I_s}{I_p}=\frac{U_p}{U_s}=\frac{36*10^3}{400}= 90=>n=90\\b)\frac{N_p}{N_s}=\frac{U_p}{U_s}=>N_p=\frac{N_sU_p}{U_s}=\frac{300*36*10^3}{400}=300*90=27000 spire=>N_p=27000 spire[/tex]
