The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an $$AC$$ supply of $$20\,V-50\,Hz.$$   The secondary will have an output of

Solution :
The transformer converts $$AC$$ high voltage into $$AC$$ low voltage, but it does not cause any change in frequency.
The ratio of voltage across input with output voltage is given by
$$\frac{{{V_s}}}{{{V_p}}} = \frac{{{N_s}}}{{{N_p}}}$$
$${{N_s}} =$$  No. of turns in secondary coil
$${{N_p}} =$$  No. of turns in primary coil
Making substitution, we obtain
$$\eqalign{ & {V_s} = \frac{{{N_s}}}{{{N_p}}}{V_p} \cr & = \frac{{5000}}{{500}} \times 20 \cr & = 200\,V \cr} $$
Thus, output has voltage $$200\,V$$  and frequency $$50\,Hz.$$