Question

An ideal transformer has 100 turns in the primary and 250 turns in the secondary. The peak value of the ac is 28 V. The r.m.s. secondary voltage is nearest to [MP PMT 1992]
A) 50 V B) 70 V C) 100 V D) 40 V

Answer 1

Given,
An ideal transformer has 100 turns in the primary and 250 turns in the secondary.
e.g., primary turns , Np = 100
secondary turns , Ns = 250
Peak value of ac = 28V
∵ peak value = √2 Rms value
∴ rms value in primary , Vp= 28/√2 = 14√2
RMS secondary voltage, Vs = ?

Use the relation,
Ns/Np = Vs/Vp
250/100 = Vs/14√2
Vs = 2.5 × 14√2 V ≈ 50V

Hence, answer is option (A)