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Topic Question Set

Q 11 :    

Which of the following circuits represents a forward biased diode?           [2025]

Choose the correct answer from the options given below:

  • (B), (D) and (E) only

     

  • (A) and (D) only

     

  • (B), (C) and (E) only

     

  • (C) and (E) only

     

(3)

For forward bias potential of p side should be higher than n side.

 

Q 12 :    

Refer to the circuit diagram given in the figure, which of the following observations are correct?             

A. Total resistance of circuit is 6 Ω.

B. Current in Ammeter is 1 A.

C. Potential across AB is 4 Volts.

D. Potential across CD is 4 Volts.

E. Total resistance of the circuit is 8 Ω.

Choose the correct answer from the options given below:                   [2025]

  • A, B and D only

     

  • A, C and D only

     

  • B, C and E only

     

  • A, B and C only

     

(1)

Current through ammeter=1 A

Rnet=6 Ω

VAB=0.5×4=2 volt

VCD=1×4=4 volt

A, B and D are correct.

Q 13 :    

What is the current through the battery in the circuit shown below?                [2025]

  • 1.0 A

     

  • 1.5 A

     

  • 0.5 A

     

  • 0.25 A

     

(3)

Both diodes are in forward bias therefore

hence Req=10 Ω

i=VR=510=12A

Q 14 :    

Consider the following statements:                                                     

A.  The junction area of solar cell is made very narrow compared to a photo diode.
B.  Solar cells are not connected with any external bias.
C.  LED is made of lightly doped p–n junction.
D.  Increase of forward current results in continuous increase of LED light intensity.
E.  LEDs have to be connected in forward bias for emission of light.

Choose the correct answer from the options given below:                           [2025]

  • B, D, E only

     

  • A, C only

     

  • A, C, E only

     

  • B, E only

     

(4)

LED is connected in forward bias and its intensity increases up to certain value of current and further there is no change as intensity saturates.

Also solar cells are not connected with any external bias. So ‘B’ is also correct.

 

Q 15 :    

In the circuit shown here, assuming threshold voltage of diode is negligibly small, then voltage VAB is correctly represented by:            [2025]

  • VAB would be zero at all times

     

  •  

  •  

  •  

(4)

Due to the diode the current will be allowed only along B to A through the resistor. Hence VAB will have only negative values i.e., the following graph represents the output voltage VAB.

 

Q 16 :    

A zener diode with 5 V zener voltage is used to regulate an unregulated dc voltage input of 25 V.  

For a 400 Ω resistor connected in series, the zener current is found to be 4 times load current. The load current (IL) and load resistance (RL) are:      [2025]  

  • IL=20 mA;  RL=250 Ω

     

  • IL=10 A;  RL=0.5 Ω

     

  • IL=0.02 mA;  RL=250 Ω

     

  • IL=10 mA;  RL=500 Ω

     

(4)

5IL=(25-5)400=120=50 mA

IL=10 mA

5=ILRL

RL=5IL=510×10-3=500 Ω

Q 17 :    

In the following circuit, the reading of the ammeter will be (Take Zener breakdown voltage = 4V)              [2025]

  • 24 mA

     

  • 80 mA

     

  • 10 mA

     

  • 60 mA

     

(3)

V1=400100+400×12V=45×12=485V

Here, V1>V2

So, Zener breakdown will be taking place.

Hence, voltage across 400 Ω will be 4V

I=4400A=1100A=10 mA

Q 18 :    

The output voltage in the following circuit is (Consider ideal diode case)                 [2025]

  • 10 V

     

  • 0 V

     

  • + 5 V

     

  • - 5 V

     

(2)

Here D1 is reverse biased and D2 is forward biased. Therefore, current flows through D2 and 5 V drop on resistor. So, Vout=0