Question

In a centre tap full wave rectifier, if Vm is the peak
voltage between centre tap and one end of the
secondary, the maximum voltage coming across the
reverse bias diode is
Options
Vm
O 2Vm
O Vm/2
O Vm/4
Clear Response​

Answer 1

Answer:Vm

Explanation:

Answer 2

Answer:

The maximum voltage coming across the reverse bias diode is $2V_m$.

Explanation:

Full wave rectifier:

• A full wave rectifier consists of two diodes and a resistor.
• The transformer in a full wave rectifier have a centre-tapped secondary winding that has a lead attached to the centre of the winding.
• The voltage from the centre tap to either end of the winding is equal to half of the total voltage between the two ends.
• For every half cycle, the polarity of the secondary voltage changes .
• Given, the peak load voltage for the full wave rectifier is $V_m$.
• The full wave rectifier produces twice as many output pulses as the half wave rectifier.
• Therefore, the  average  load  voltage is  $V_{avg}=2V_m$
• When a diode is reverse biased, the peak voltage across that diode will be equal to $V_m$.  
• Let $D_1$ is conducting and $D_2$ is reverse biased.  
• The cathode of $D_1$ is at $V_m$ and since it is directly connected to the cathode of $D_2$, it is also  equal to $V_m$.  
• Thus, there will be negative $V_m$ applied to the anode of $D_2$, and hence the total voltage across the diode $D_2$ is $2V_m$.
• Therefore, the maximum reverse voltage across either diode will be twice the peak load voltage, $V_{p}=2V_m$

Therefore, the correct answer is option 1.