Question

In a full wave junction diode rectifier the input ac has rms value of $20V$. The transformer used is a step up transformer having primary and secondary turn ratio $1:2$. The dc voltage in the rectified output is

• A. $12V$
• B. $24V$
• C. $36V$
• D. $42V$

Answer 1

Answer: (C)

Here, input $V_{rms}=20V$
Peak value of input voltage
$V_0=\sqrt{2}{V}_{rms}$
$=\sqrt{2}\times 20$
$=28.28V$
Since the transformer is a step up transformer having transformer ratio $1:2$, the maximum value of output voltage of the transformer applied to the diode will be
$V_0^{\prime }=2\times V_0$
$=2\times 28.28V$
$\therefore$ dc voltage $=\frac{2V_0^{\prime }}{\pi }$
$=\frac{2\times 2\times 28.28}{22/7}$
$=36V$