250+ TOP MCQs on Filters-2 and Answers

Power Electronics Multiple Choice Questions & Answers (MCQs) on “Filters-2”.

1. A diode rectifier with a C filter will have average output voltage _______ than that obtained by a rectifier without the C filter.
A. lower than
B. higher than
C. same as
D. none of the mentioned
Answer: B
Clarification: C filter improves the efficiency and eliminates ripples by keeping the output voltage constant.

2. An inductor filter connected in series with a resistive load provides a
A. smoothing of the output voltage waveform
B. smoothing of the input voltage waveform
C. smoothing of the output current waveform
D. smoothing of the input current waveform
Answer: C
Clarification: Filter is always connected to the load side (output). Inductor has the property of keeping the current smooth and constant.

3. In the below given configuration, L is connected as a filter across the R load.

The average ammeter current is
A. 2Vm/R
B. 2Vm/πR
C. Vm/πR
D. Vm/R
Answer: B
Clarification: I = Vo/R
Vo = 2Vm/π.

4. The current ripple factor (CRF) is the ratio of
A. Average value/RMS value
B. RMS value/Average value
C. Average value/Maximum value
D. Maximum value/RMS value
Answer: B
Clarification: CRF = Ir/Io.

5. In case of an L filter, the ripple current increases with
A. increase in Load
B. decrease in Load
C. increase in the value of L
D. ripple current never increases
Answer: B
Clarification: When the load is reduced the resistance R is increased & ripple current increases.

6. In case of a C filter, if R (load resistance) is increased
A. ripple factor is reduced
B. ripple factor is increased
C. ripple factor is not affected
D. increases noise in the circuit
Answer: A
Clarification: The time constant RC is increased therefore the ripple factor is reduced.

7. When a certain type of filter is connected across the R load, of a full wave bridge diode biased rectifier the following output current waveform is obtained.

The filter connected is most likely a
A. L filter
B. C filter
C. LC filter
D. None of the above mentioned
Answer: A
Clarification: The above waveform is that of the output current. The peak per half cycle is on the right, hence it is more likely to be an L filter.

8. C filters are suitable for ___________ load resistances and L filters are suitable for _____________ load resistances.
A. low, low
B. high, high
C. high, low
D. low, high
Answer: C
Clarification: In case of L filter, if R is lowered, the time constant (L/R) increases, therefore ripple factor reduces. In case of a C filter, the time constant RC is increased, therefore, ripple factor is reduced.

9. An LC filter will have ripple factor value___________ (For the same value of L & C.
A. lower than that obtained by L filter but higher than that obtained by C filter
B. lower than that obtained by C filter but higher than that obtained by L filter
C. lower than that obtained by either L or C filter
D. higher than that obtained by either L or C filter
Answer: C
Clarification: Simply, an LC filter combines both the advantages of L and C filters.

10. In a single-phase full wave rectifier ___________ order harmonics are the most dominant
A. first
B. second
C. third
D. fourth
Answer: B
Clarification: The output voltage is given by,
Vo = (2Vm/π) – (4Vm/3π)cos 2ωt – (4Vm/15π)cos 4ωt . . . .
Hence the other values after the second factor (4Vm/3π) become very very small hence they can be eliminated.