Given ,

primary voltage Vp = 220 V

primary turns Np = 2000 turns

secondary turns Ns = ? ?

Secondary voltage Vs = 45 V

Using formula,

\(\frac{Vp}{Vs}=\frac{Np}{Ns}\)

\(\frac{220}{45}=\frac{2000}{Ns}\)

Ns = 409 .09 turns

Therefore , the secondary coil in the transformer has 409 turns.