Power Electronics Question and Answers – 1P-Diode Rectifier HW-2

This set of Power Electronics Multiple Choice Questions & Answers (MCQs) focuses on “1-Phase-Diode Rectifiers HW-2”.

1. A 1-phase 230V, 1KW heater is connected across a 1-phase HW rectifier (diode based). The power delivered to the heater is
a) 300 W
b) 400 W
c) 500 W
d) 600 W
View Answer

Answer: c
Explanation: R = (230 x 230)/1000
V(rms) = (√2 x 230)/2
P = V(rms)2/R = 500W.

2. A 1-phase half wave diode rectifier with R load, has input voltage of 240 V. The input power factor is
a) Unity
b) 0.707 lag
c) 0.56 lag
d) 0.865 lag
View Answer

Answer: c
Explanation: Input p.f = V(rms)/Vs
Vrms is the RMS value of output voltage. Vrms = (√2 x 230)/2
Vs = 230
pf = 0.707.

3. A 1-phase half wave diode rectifier with R = 1 KΩ, has input voltage of 240 V. The diode peak current is
a) Zero
b) 240mA
c) 24mA
d) 0.24mA
View Answer

Answer: b
Explanation: Diode peak current = peak current through the load = Vo/R = Vm/2R.
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4. For the below given circuit, after the switch is closed the voltage across the load (shown open) remains constant.
The element across the load would be a/an capacitor for all initial conditions are zero
Assuming that all initial conditions are zero. The element across the load would be a/an
a) resistor
b) capacitor
c) inductor
d) data not sufficient
View Answer

Answer: b
Explanation: As the voltage remains constant as soon as the switch is closed, the element is most likely to be a capacitor.

5. For the below given circuit,
After the supply voltage (Vs) given diode starts conducting only when Vs exceeds Vdc
After the supply voltage (Vs) is given the
a) diode starts conducting
b) diode starts conducting only when Vs exceeds Vdc
c) diode never conducts
d) diode stops conducting only when Vs exceeds Vdc
View Answer

Answer: b
Explanation: The diode will be forward biased only when Vs will be greater than Vdc.
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6. For the below given circuit,
The expression for the average voltage is Vm/π
With Vs = Vm sin ωt (secondary side). The expression for the average voltage is
a) Vm
b) Vm/2π
c) Vm/π
d) Vm/2
View Answer

Answer: c
Explanation: Due to the FD, we get 1st quadrant operation.
Where, output voltage (Avg) = 1/2π [ ∫Vm sin ωt d(ωt) ], integration runs from 0 to 180 degrees.

7. For the below given circuit, the
The output voltage is the voltage across the resistor & Vdc
a) output voltage is never positive
b) output current is never positive
c) output current is never zero
d) output voltage is never zero
View Answer

Answer: d
Explanation: The output voltage is the voltage across the resister and Vdc. Even if the current falls to zero, the output voltage will be equal to Vdc.
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8. For the below given circuit,
The ripple voltage is 125.32 V in given figure
Vs = 325 sin ωt (secondary side)
The ripple voltage is
a) 125.32 V
b) 255.65 V
c) 325 V
d) 459.12 V
View Answer

Answer: a
Explanation: Ripple voltage = √(Vrms2 + Vavg2)
Vrms = Vm/2
Vavg = Vm/π

9. For a single phase half wave rectifier, the rectifier efficiency is always constant & it is
a) 4/π2
b) 8/π2
c) 100
d) 2/π2
View Answer

Answer: a
Explanation:
Rectifier efficiency = Pdc/Pac
Pdc = (Vm x Im)/π2
Pac = 4/(Vm x Im).
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10. For the below given circuit,
The output voltage is the voltage across the resistor & Vdc
The power delivered to the load in Watts is
a) I(avg).Vdc
b) I(avg).Vdc + I(rms)2.R
c) I(avg).Vdc – I(rms)2.R
d) I(avg).Vdc + I(avg)2.R
View Answer

Answer: b
Explanation: P = power delivered to the resister + power delivered to the emf source.

Sanfoundry Global Education & Learning Series – Power Electronics.

To practice all areas of Power Electronics, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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