A) 5 : 8
B) 8 : 5
C) 4 : 5
D) 5 : 4
Correct Answer: C
Solution :
If \[{{i}_{p}}\] and \[{{i}_{s}}\] be the currents in the primary and secondary coils at any instant, and the energy losses be zero, then power in secondary = power in primary \[{{V}_{s}}\times {{i}_{s}}={{V}_{p}}\times {{i}_{p}}\] \[\Rightarrow \] \[\frac{{{i}_{p}}}{{{i}_{s}}}=\frac{{{V}_{s}}}{{{V}_{p}}}=\frac{{{N}_{s}}}{{{N}_{p}}}=r\] \[\Rightarrow \] \[{{V}_{s}}=\frac{{{N}_{s}}}{{{N}_{p}}}\times {{V}_{p}}\] Given, \[{{V}_{p}}=220\,V,\,{{N}_{p}}=5,\,{{N}_{s}}=4\] \[\therefore \] \[{{V}_{s}}=\frac{4}{5}\times 220=176\,V\] Ratio of currents \[\frac{{{i}_{p}}}{{{i}_{s}}}=\frac{{{V}_{s}}}{{{V}_{p}}}=\frac{176}{220}=\frac{4}{5}\]
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