EE AND ECE IMPORTANT MCQ-RECTIFIERS AND FILTERS

l. In a half – wave
rectifier, the load current flows
for                                                               
(a)    Complete cycle of the input signal
(b)   Less than half-cycle of the input signal,
(c)    More than half-cycle but less than complete cycle of the
input signal.
(d)   Only for the positive half-cycle of the input signal.
                           ANS-d
2.     
In a full-wave
rectifier, the current in each of the diodes
flows for                                        

                       (a)    Complete cycle of the
input signal.      (b) Half cycle of the input signal.

(c)  Less than half
of the input signal.        (d) None of
the above.
                      ANS-b 
3.  The ripple
factor of a bridge rectifier is                                                                                      
(a)
0.482                        (b) 0.8l2            (c) l.ll            (d)
l.2l

ANS-a
4.   A bridge rectifier
is preferable to an ordinary two-diode full-wave rectifier because              
(a)    It needs much smaller transformer for the same output.
(b)   It uses four diodes.
(c)    Its transformer does not require center-tap.
      (d)   None of the above.
                            ANS-a
5. The basic purpose of
a filter is to                                                                                           
(a)    Minimize variations in a.c. input signal.
      (b)   Suppress harmonics in rectified output.
(c)    Remove ripples from the rectified output.
(d)   Stabilize d.c. output
voltage.
                           ANS-c

6. The use of a capacitor filter
in a rectifier circuit gives satisfactory performance only when the load

(a) Current is high                    (b)
current is low
(c) Voltage is high                    (d)
voltage is low
ANS-b
7. A half-wave rectifier is equivalent to a
(a) a clamper circuit                             (b)
a clipper circuit
(c)
a clamper circuit with negative bias  (d) a clamper circuit with positive bias
ANS-b
8. Bridge rectifiers are preferred because
(a)  they require small transformer
(b)  they have less peak-inverse voltage
(c)  they need small transformer and also have
less peak-inverse voltage
                            (d)   
They have low ripple
factor.

ANS-c
9. If Vm is the
peak value of an applied voltage in a half-wave rectifier with a large
capacitor across the load, then the
peak-inverse voltage will be                                                                          

(a)v                  (b)Vm              (c) 1     (d) 2
               ANS-a
l0.
A voltage of is applied
to a half-wave rectifier with a load resistance of 5K. The rectifier is represent by an ideal diode in series with a
resistance of l K. The maximum value of current, d.c.
component of current and r.m.s.
value of current
will be respectively                                                  

(a)
33.33 mA, l0.6l
mA and l6.67mA                 (b) 22.22
mA, 8.6l mA and l2.38
mA
(c) 
28.33 mA, l4.6l mA and l3.33 mA              (d) 40 mA, 20 mA and 25 mA
                ANS-a 
 ll. The basic reason
why a full-wave rectifier has a twice the efficiency of a half-wave rectifier
is that
(a)    it makes use of transformer                                                                                        
(b)   its ripple factor is much less
(c)    it utilizes both half-cycle of the input
(d)   its output frequency is double the line frequency.
                           ANS-c
  
l2.  The output of
a half-wave rectifier is suitable only for                                                           

(a) running car radios               (b)
running a.c. motors
(c) 
charging batteries                (d)
running tape recorders.
                ANS-b

l3. The ripple factor of a bridge rectifier is                                                                                     

  (a) 0.406               (b) 0.8l2           (c) l.2l                                       (d) l.ll

  ANS-c

l4.  The ripple
factor of a power supply is given by (symbols have the usual meaning).              

(a) √FF²-1        (b)Irm/Idc        (c)Idc/Irm    (d) FF²-1
            ANS-a

l5.  The PIV of a Full-wave
center tap  rectifier circuit is                                                               (a)V            (b)Vm              (c)2Vm            (d)
3

 ANS-c
l6.
The
primary function of a rectifier filter is to
(a)  minimise a.c. input variations
(b)  suppress odd harmonics in the rectifier
output
(c)  stabilise d.c, level of the output voltage
(d)  remove ripples from the rectified output
                      ANS-d


 l7.  In a
rectifier, larger the value of shunt capacitor filter                                                            

a.      
larger the
peak-to-peak value of ripple voltage
b.     
larger the peak
current in the rectifying diode
c.      
longer the time that
current pulse flows through the diode
d.     
Smaller the d.c.
voltage across the load.
                           ANS-b

l8.
In a LC filter, the ripple factor                                                                                                 

(a) Increases with the
load current                   (b) increases with the load resistance
(c) Remains constant with the load current        (d) has the lowest value.
                 ANS-c

l9.
The main reason why a bleeder resistor
is used in a d.c. power supply is that it                          

(a) Keeps the supply ON                     (b)
improves voltage regulation
(c) Improves filtering action                  (d)
both (b) and (c).
         ANS-d
20. 
Which rectifier
requires four diodes?                                                                                      
(a) 
half-wave voltage
doubler  (b) full-wave voltage doubler
(c) full-wave bridge circuit      (d)
voltage quadrupler.
                ANS-b

2l. If, by
mistake, a.c source in a bridge rectifier, is connected across the d.c.
terminals, it will burn out and hence short                        diodes.                                                                                          

(a) one             (b) two             (c) three           (d) four
               ANS-d
22.  The d.c. output polarity from a half-wave rectifier can
be reversed by reversing                    
(a) 
The diode                           (b)
transformer primary
(c) Transformer
secondary       (d) both (b) and (c).
               ANS-a
23.  In a half-wave rectifier if a resistance equal to load resistance is connected in parallel with the diode,
then
(a) 
Output voltage would be halved     (b) output voltage would be doubled                          
(c) Circuit will stop rectifying              (d) output voltage will remain unchanged,
               ANS-c

24.  If the input supply frequency is 50 Hz, the output ripple
frequency of a bridge rectifier is                                 Hz.

(a)  l00         (b)
75   (c) 50   (d) 25.
                ANS-a

 

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