250+ TOP MCQs on Filters-I and Answers

Power Electronics Multiple Choice Questions on “Filters-1”.

1. In practice the output from the diode rectifier has
A. AC component only
B. DC component only
C. AC + DC component
D. None of the mentioned
Answer: C
Clarification: The output contents along with the DC components the AC harmonics which does no useful work & reduces the efficiency.

2. Choose the correct statement
A. The AC component in the output of rectifier does the useful work
B. The AC component in the output of rectifier increases the efficiency of the system
C. The AC component in the output of rectifier causes ohmic losses
D. The AC component in the output of rectifier does not affect the operation
Answer: C
Clarification: A rectifier is used to convert AC to DC. Lower the AC (Non-DC. components in the output lower are the ohmic losses.

3. An L filter is connected ________
A. in series
B. in parallel
C. in both series and parallel
D. none of the mentioned
Answer: A
Clarification: Inductor (L) has a very important property that the current through it cannot change rapidly. We can make use of this property by connecting it in series.

4. In case of an L filter connected with a rectifier in series with the load, it offers ________ impedance to ac whereas _______ resistance to dc respectively.
A. high, high
B. high, low
C. low, high
D. low, low
Answer: B
Clarification: It offers high impedance to AC such as the AC ripples do not pass through the load.

5. In case of a C filter, the AC is not allowed to pass to the load by
A. offering it high impedance
B. offering it low impedance
C. short circuiting the AC component
D. open circuiting the AC component
Answer: C
Clarification: AC ripples are not allowed to pass, by S.C the AC ripples as the C is always connected in parallel with the load.

6. A capacitor filter or C filter can be used in a rectifier by connecting it
A. in parallel with the load
B. in series with the load
C. in parallel with the supply
D. in series with the supply
Answer: A
Clarification: AC ripples are not allowed to pass, by S.C the AC ripples as the C is always connected in parallel with the load.

7. Examine the below shown circuit.

While D7 & D10 are reversed biased the
A. capacitor is charging through Vs
B. capacitor is discharging through Vs
C. capacitor is charging through R
D. capacitor is discharging through R
Answer: D
Clarification: When the two are reversed biased and the other two SCR’s are not yet gated, the stored energy in the capacitor is supply the load R.

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

The filter connected is most likely to be a/an
A. L filter
B. C filter
C. LC filter
D. None of the above mentioned
Answer: B
Clarification: It is to be noted that the waveform is that of a voltage parameter. The voltage goes up for a very small time and than goes down (discharges) for longer time. For every half wave the peak of the waveform is to the left, if it were to be on the right it would be more likely to be a L filter.

9. For the below given circuit,

When the output current rises, the capacitor current
A. is increasing
B. is decreasing
C. is constant
D. is zero
Answer: B
Clarification: When the load current is increasing, the capacitor is charging through the source voltage & its current keeps on falling & voltage rises.

10. A single-phase diode B-2 rectifier is fed from a 250 V, 50 Hz source & connected to a load of R = 400 Ω.
Design a capacitor filter such that the ripple factor of the output voltage is less than 5 %. Find the value of the capacitance of the C filter.
A. 156.4 μF
B. 500 μF
C. 189 μF
D. 246 μF
Answer: C
Clarification: Use,
C = K * [1 + 1/√2RF]
Where, K = 1/4fR.