SSC JE Electrical Engineering 2017 Set 3 Paper

Relation to a transformer the ratio 20 : 1 indicates at every 20 primary turn there is one secondary turn
${\mathit{N}}_1{\mathit{I}}_1={\mathit{N}}_2{\mathit{I}}_2$
MMF should balance in a magnetic circuit
Let ${\mathit{I}}_1=\frac{{\mathit{N}}_2}{{\mathit{N}}_1}{\mathit{I}}_2$
Now $\frac{{\mathit{N}}_1}{{\mathit{N}}_2}=\frac{20}{1}$
∴ ${\mathit{I}}_1=\frac{1}{20}{\mathit{I}}_2$
So secondary current is 20 times the primary.