In the circuit of figure the function of resistor R and diode D are to limit the

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Question
In the circuit of figure the function of resistor R and diode D are
Options
A. to limit the current and to protect LED against over voltage
B. to limit the voltage and to protect LED against over current
C. to limit the current and protect LED against reverse breakdown voltage.
D. none of the above.

Correct Answer

to limit the current and protect LED against reverse breakdown voltage.

Explanation

Resistance limits current and diode is reverse connected and therefore protects LED against reverse breakdown.

Electronic Devices and Circuits problems

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1. At room temperature the current in an intrinsic semiconductor is due to
Options
A. holes
B. electrons
C. ions
D. holes and electrons

2. The amount of photoelectric emission current depends on
Options
A. frequency of incident radiation
B. intensity of incident radiation
C. both frequency and intensity of incident radiation
D. none of the above

3. In p-n-p transistor the current I_E has two components viz. I_EP due to injection of holes from p-region to n-region and I_E due to injection of electrons from n-region to p-region. Then
Options
A. I_Ep and I_En are almost equal
B. I_Ep >> I_En
C. I_En >> I_Ep
D. either (a) or (c)

4. In an n-p-n transistor, the majority carriers in the base are
Options
A. electrons
B. holes
C. both holes and electrons
D. either holes or electrons

5. A zener diode is used in
Options
A. voltage regulator circuit
B. amplifier circuits
C. both voltage regulator and amplifier circuit
D. none of the above

6. In a bipolar transistor which current is largest
Options
A. collector current
B. base current
C. emitter current
D. base current or emitter current

7. Assertion (A): The conductivity of p type semiconductor is higher than that of intrinsic semiconductor.
Reason (R): The addition of donor impurity creates additional energy levels below conduction band.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true

8. A transistor has two p-n junctions. The batteries should be connected such that
Options
A. both junctions are forward biased
B. both junctions are reverse biased
C. one junction is forward biased and the other is reverse biased
D. none of the above

9. A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode is
Options
A. 100
B. 99
C. 1.01
D. 0.99

10. A p-n junction diode has
Options
A. low forward and high reverse resistance
B. a non-linear v-i characteristics
C. zero forward current till the forward voltage reaches cut in value
D. all of the above

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