Output voltage, \(V_{s}=440\, \mathrm{V}\) 

Input current, \(I_{p}=?\) 

Output current, \(I_{s}=2\, \mathrm{A}\) 

Efficiency of the transformer, \(\eta=80 \%\)

Efficiency of the transformer, \(\eta=\frac{\text { Output power }}{\text { Input power }}\)

\(\eta=\frac{V_{s} I_{s}}{V_{p} I_{p}} \quad\) or \(\quad I_{p}=\frac{V_{s} I_{s}}{\eta V_{p}}=\frac{(440\, \mathrm{V})(2 \,\mathrm{A})}{\left(\frac{80}{100}\right)(220 \,\mathrm{V})}\)

\(=\frac{(440\, \mathrm{V})(2\, \mathrm{A})(100)}{(80)(220\, \mathrm{V})}=5\, \mathrm{A}\)