Question 8: In a ideal transformer, the turns ratio \frac{\mathrm{N}_{\mathrm{p}}}{\mathrm{N}_{\mathrm{s}}}=\frac{1}{2}. The ratio \mathrm{V}_{\mathrm{s}}: \mathrm{V}_{\mathrm{p}} is equal to (the symbols carry their usual meaning) :
(1) 1: 2
(2) 2: 1
(3) 1: 1
(4) 1: 4
Answer: Option (2)
Explanation:
In an ideal transformer, the ratio of voltages across the secondary
and primary coils is equal to the ratio of the number of turns in the secondary and primary coils.
This relation is given by \frac{V_{s}}{V_{p}}=\frac{N_{s}}{N_{p}}.
Given that \frac{N_{p}}{N_{s}}=\frac{1}{2}, taking reciprocal we get
\frac{N_{s}}{N_{p}}=2.
Substituting this value in the voltage ratio,
\frac{V_{s}}{V_{p}}=2.
Hence, the ratio V_{s}:V_{p}=2:1.
Therefore, the correct answer is option (2).