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ESE EC : Electronic Devices & Circuits - National Champion Test

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Question 1

Match List-I (Current) with List-II (Variation) and select the correct answer using the code given below the lists:
List I
A) Hole diffusion current
B) Electron drift current
C) Hole drift current
D) Electron diffusion current
List II
1)
2)
3)
4)

Question 2

Why does the mobility of electrons in a semiconductor decrease with increasing donor density?

Question 3

In a homogeneously doped n-type semiconductor bar, holes are injected at one end of the bar. How will the holes flow to the other end?

Question 4

Consider the following statements:
Electrical conductivity of a metal has negative temperature coefficient since
1) electron concentration increases with temperature
2) electron mobility decreases with temperature
3) electron-lattice scattering increases with temperature
Which of the statements given above are correct?

Question 5

Assertion (A): Electron mobility in metals decreases with increasing temperature.
Reason (R): In metals electron concent-ration is high.

Question 6

A Si sample is doped with a fixed number of group V impurities. The electron density n is measured from 4 K to 1200 K for the sample. Which one of the following is correct?

Question 7

Match List-I (Material) with List-II (Energy Level) and select the correct answer using the code given below the lists:
List-I
A) p-type semiconductor at 0K temperature
B) Intrinsic semiconductor at 0K temperature
C) n-type semiconductor at room temperature
D) p-type semiconductor at room temperature
List-II
1) Donor energy level is close to the conduction band
2) Acceptor energy level is close to the valence band
3) Fermi-level is very close to valence band
4) Fermi-level is half-way between the valence band and the conduction band

Question 8

Which of the following can be determined by using a Hall crystal?
1) Concentration of holes in a p-type semi-conductor.
2) Concentration of electrons in an n-type semi-conductor.
3) Temperature of the set-up with any type of semiconductor
4) Diffusion constant and life-time of minority carriers of any type of semiconductor
Select the correct answer using the code given below:

Question 9

The free electron density in a conductor is (1/1.6) × 1022 cm-3. The electron mobility is 10 cm2/Vs. What is the value of its resistivity?

Question 10

Which one of the following is the correct relationship between the band gap of a material used in a photo detector and the energy of the incident photon?

Question 11

An n-type semiconductor is illuminated by a steady flux of photons with energy greater than the band gap energy. The change in conductivity obeys which relation?

Question 12

Which junction has least junction capacitance?

Question 13

In addition to conduction, which one of the following mechanism can account for the transport of charges in a semiconductor (not ordinarily encountered in metals)?

Question 14

The mobility of electrons in a semiconductor is defined as the

Question 15

The electron concentration in a silicon sample doped with P atoms, will vary, in the temperature range of 4.2 – 1000 K, as follows:

Question 16

Consider a Ge diode operating at 27oC and just beyond the threshold voltage of Ge. What is the value of dV/dT?

Question 17

Mobility is defined as

Question 18

A 12 V automobile light is rated at 30 W. The total charge that flows through the filament in one minute is

Question 19

Statement (I) : Hall voltage is given by where I is the current, H is the magnetic field strength, t is the thickness of probe and RH is the Hall constant.
Statement (II): Hall effect does not sense the carrier concentration.

Question 20

For a particular material, the Hall Voltage is found to be zero. The material is

Question 21

A junction FET can be used as a voltage variable resistor

Question 22

The collector and emitter current levels for a transistor with the common base current gain of 0.99 and the base current of 20 μA are respectively.

Question 23

In a junction transistor recombination of electrons and holes occurs in

Question 24

Consider the following statements X-rays are used for lithography tn IC technology because
1) high resolution is achievable.
2) scattering effects are small.
3) they can be focussed easily
4) they can be deflected easily.
Which of the statements given above are correct?

Question 25

Why is the term ‘planer technology’ for fabrication of devices in ICs used?

Question 26

Match List-I (Semiconductor Device) with List-II (Application) and select the correct answer using the codes given below the lists:
List-I
A) Triac
B) IGBT
C) SCR
D) UJT
List-II
1) Used in HVDC system
2) Used in pulse generation
3) Used in motor control circuits
4) Used in ac regulators

Question 27

Once an SCR is turned on. it remains so until the anode current goes below:

Question 28

An SCR can be turned off

Question 29

The turn-on time of an SCR is 5 μs. Its trigger pulse should have which one of the following?

Question 30

What are the different methods followed to take p-n-p-n device from its conducting state to the non-conducting state?
1) Reducing the anode current below the holding value.
2) Reducing the gate current to zero
3) Reducing the gate voltage to zero
4) Reducing anode voltage below the holding value.
Select the correct answer using the code given below:
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Dec 16ESE & GATE EC