Exercise: Electronic Devices And Circuits

Questions for: Electronic Devices And Circuits

Assertion (A): A high junction temperature may destroy a diode.

Reason (R): As temperature increases the reverse saturation current increases.

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
Answer: A

Both A and R are correct. The diode is destroyed due to high reverse current.

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The number of p-n junctions in a semiconductor diode are
A:
0
B:
1
C:
2
D:
1 or 2
Answer: B

Semiconductor diode has one p-n junction, BJT has two and SCR has three p-n junctions.

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Discrete transistors T1 and T2 having maximum collector current rating of 0.75 amp are connected in parallel as shown in the figure, this combination is treated as a single transistor to carry a total current of 1 ampere, when biased with self bias circuit. When the circuit is switched on, T1 draws 0.55 amps and T2 draws 0.45 amps. If the supply is kept on continuously, ultimately it is very likely that
A:
Both T1, and T2 get damaged
B:
Both T1, and T2 will be safe.
C:
T1 Will get damaged and T2 will be safe
D:
T2 will get damaged and T1, will be safe.
Answer: C

T1 draws 0.55 A and T2 draws 0.45 A, T1 will get more heated and correct increase. Ultimately, I1 = 1A and I2 = 0.

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For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in illumination results in
A:
a change in O.C. voltage
B:
a change in S.C. current
C:
a decrease in resistance
D:
an increase in resistance
Answer: C

Increase in illumination reduces resistance of a photoconductor.

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In which material do conduction and valence bands overlap
A:
insulators
B:
conductors
C:
both conductor and semiconductor
D:
semiconductors
Answer: B

This is the reason for high conductivity of conductors.

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