R4RIN – MCQs, Mock Tests | Semiconductor Semiconductor Mcq Question Set 4

If a small amount of antimony is added to germanium crystal

1. it becomes a p–type semiconductor
2. the antimony becomes an acceptor atom
3. there will be more free electrons than holes in the semiconductor
4. its resistance is increased

✅ Correct Answer: 3

By increasing the temperature, the specific resistance of a conductor and a semiconductor

1. increases for both
2. decreases for both
3. increases, decreases
4. decreases, increases

✅ Correct Answer: 3

A strip of copper and another of germanium are cooled from room temperature to 80K. The resistance of

1. each of these decreases
2. copper strip increases and that of germanium decreases
3. copper strip decreases and that of germanium increases
4. each of these increases

✅ Correct Answer: 3

Carbon, Silicon and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C, (Eg)Si and (Eg)Ge respectively. Which one of the following relationship is true in their case?

1. (Eg)C > (Eg)Si
2. (Eg)C < (Eg)Si
3. (Eg)C = (Eg)Si
4. (Eg)C < (Eg)Ge

✅ Correct Answer: 1

A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be a/an

1. intrinsic semiconductor
2. p-type semiconductor
3. n-type semiconductor
4. p-n junction diode

✅ Correct Answer: 4

If the two ends of a p-n junction are joined by a wire

1. there will not be a steady current in the circuit
2. there will be a steady current from the n-side to the p side
3. there will be a steady current from the p-side to the n side
4. there may or may not be a current depending upon the resistance of the connecting wire

✅ Correct Answer: 1

The drift current in a p-n junction is from the

1. n-side to the p-side
2. p-side to the n-side
3. n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse biased
4. p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

✅ Correct Answer: 1

The diffusion current in a p-n junction is from the

1. n-side to the p-side
2. p-side to the n-side
3. n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse-biased
4. p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

✅ Correct Answer: 2

Diffusion current in a p-n junction is greater than the drift current in magnitude

1. if the junction is forward-biased
2. if the junction is reverse-biased
3. if the junction is unbiased
4. in no case

✅ Correct Answer: 1

Forward biasing is that in which applied voltage

1. increases potential barrier
2. cancels the potential barrier
3. is equal to 1.5 volt
4. None of these

✅ Correct Answer: 2

In V-I characteristic of a p-n junction, reverse biasing results in

1. leakage current
2. the current barrier across junction increases
3. no flow of current
4. Large current flow

✅ Correct Answer: 1

In reverse biasing

1. large amount of current flows
2. potential barrier across junction increases
3. depletion layer resistance increases
4. no current flows

✅ Correct Answer: 2

Filter circuit

1. eliminates a.c. component
2. eliminates d.c. component
3. does not eliminate a.c. component
4. None of these

✅ Correct Answer: 1

For a junction diode the ratio of forward current (If) and reverse current (Ir) is [e = electronic charge, V = voltage applied across junction, k = Boltzmann constant, T = temperature in kelvin]

1. e–V/kT
2. eV/kT
3. (e–eV/kT + 1)
4. (eeV/kT – 1)

✅ Correct Answer: 4

In a semiconductor diode, the barrier potential offers opposition to

1. holes in P-region only
2. free electrons in N-region only
3. majority carriers in both regions
4. majority as well as minority carriers in both regions

✅ Correct Answer: 3

In a P -N junction

1. the potential of P & N sides becomes higher alternately
2. the P side is at higher electrical potential than N side.
3. the N side is at higher electric potential than P side.
4. both P & N sides are at same potential.

✅ Correct Answer: 2

Barrier potential of a P-N junction diode does not depend on

1. doping density
2. diode design
3. temperature
4. forward bias

✅ Correct Answer: 2

Reverse bias applied to a junction diode

1. increases the minority carrier current
2. lowers the potential barrier
3. raises the potential barrier
4. increases the majority carrier current

✅ Correct Answer: 3

In forward biasing of the p–n junction

1. the positive terminal of the battery is connected to p–side and the depletion region becomes thick
2. the positive terminal of the battery is connected to n–side and the depletion region becomes thin
3. the positive terminal of the battery is connected to n–side and the depletion region becomes thick
4. the positive terminal of the battery is connected to p–side and the depletion region becomes thin

✅ Correct Answer: 4

When p-n junction diode is forward biased then

1. both the depletion region and barrier height are reduced
2. the depletion region is widened and barrier height is reduced
3. the depletion region is reduced and barrier height is increased
4. Both the depletion region and barrier height are increased

✅ Correct Answer: 1

The cause of the potential barrier in a p-n junction diode is

1. depletion of positive charges near the junction
2. concentration of positive charges near the junction
3. depletion of negative charges near the junction
4. concentration of positive and negative charges near the junction

✅ Correct Answer: 4

The ratio of forward biased to reverse biased resistance for p-n junction diode is

1. 10–1 : 1
2. 10–2 : 1
3. 104 : 1
4. 10–4 : 1

✅ Correct Answer: 4

In the middle of the depletion layer of a reverse- biased p-n junction, the

1. electric field is zero
2. potential is maximum
3. electric field is maximum
4. potential is zero

✅ Correct Answer: 3

Bridge type rectifier uses

1. four diodes
2. six diodes
3. two diodes
4. one diode

✅ Correct Answer: 1

The average value of output direct current in a half wave rectifier is

1. I0/π
2. I0/2
3. π I0/2
4. 2 I0/π

✅ Correct Answer: 1

The average value of output direct current in a full wave rectifier is

1. I0/π
2. I0/2
3. π I0/2
4. 2 I0/π

✅ Correct Answer: 4

In a half wave rectifier, the r.m.s. value of the a.c. component of the wave is

1. equal to d.c. value
2. more than d.c. value
3. less than d.c. value
4. Zero

✅ Correct Answer: 4

In an intrinsic semiconductor, the Fermi level

1. Lies at the center of forbidden energy gap.
2. Is near the conduction band.
3. Is near the valence band.
4. May be anywhere in the forbidden energy gap.

✅ Correct Answer: 4

The ratio of impurity atoms to intrinsic semiconductor atoms in an extrinsic semiconductor is about.

1. 1:10
2. 1:103
3. 1:105
4. 1:10

✅ Correct Answer: 4

In a P type material the Fermi level is 0.3 eV above the valence band. The concentration of accepter atoms is increased. The new position of Fermi level is likely to be

1. 0.5 eV above the valence band.
2. 0.2 eV above the valence band.
3. Below the valence band.
4. None of the above.

✅ Correct Answer: 2

Most commonly used semiconductor material is

1. Silicon
2. Germanium
3. Mixture of silicon and germanium
4. None of the above.

✅ Correct Answer: 1

At room temperature a semiconductor material is

1. . Perfect insulator
2. Conductor
3. Slightly conducting
4. Any one of the above.

✅ Correct Answer: 3

For silicon, the energy gap at 300 K is

1. 1.1 W
2. 1.1 J
3. 1.1 eV
4. None of these

✅ Correct Answer: 3

The forbidden gap for germanium is

1. 0.12 eV
2. 0.72 eV
3. 7.2 eV
4. None of These

✅ Correct Answer: 2

The process of adding impurities to a pure semiconductor is called

1. Mixing
2. Doping
3. Diffusing
4. None of the above

✅ Correct Answer: 2

The pentavalent impurities like antimony, arsenic, bismuth and phosphorus, added to intrinsic semiconductors are called

1. Acceptor or P-type impurities
2. Donor or P-type impurities
3. Acceptor or N-type impurities
4. Donor or N-type impurities

✅ Correct Answer: 4

Impurities like boron, aluminum, gallium or indium are added to intrinsic semiconductor to form

1. N-type doped semiconductor
2. P-type doped semiconductor
3. A junction diode
4. All of these are risks involved in development.

✅ Correct Answer: 2

In a N-type semiconductor, the position of Fermi-level

1. Is lower than the center of energy gap
2. Is at the center of energy gap
3. Is higher than the center of energy gap
4. Can be any where

✅ Correct Answer: 3

The mobility of electrons in a material is expressed in unit of:

1. V/s
2. m2 /V-s
3. m 2 /s
4. J/K

✅ Correct Answer: 2

In a metal

1. The electrical conduction is by electrons and holes
2. The conductivity decreases with the rise in temperature
3. The conduction band is empty
4. . None of the above

✅ Correct Answer: 2

The energy gap in a semiconductor

1. Increases with temperature
2. Does not change with temperature
3. Decreases with temperature
4. Is zero

✅ Correct Answer: 3

Two initially identical samples A and B of pure germanium are doped with donors to concentrations of 1x1020 and 3x1020respectively. If the hole concentration in A is 9x1012, then the hole concentration in B at the same temperature will be

1. 3x1012 m-3
2. 7x1012 m-3
3. 11x1012 m-3
4. 27x1012 m-3

✅ Correct Answer: 1

Which one of the following statement(s) is true?

1. Resistivity of conductors increases with increase in temperature.
2. Resistivity of semiconductors increases with increase in temperature
3. Resistivity of semiconductors decreases with increase n temperature.
4. Resistivity of insulators decreases with decrease in temperature

✅ Correct Answer: 1

The forbidden energy gap Eg in case of semiconductors is of the order of

1. 6 eV
2. 1 eV
3. 0.1 eV
4. None of the mentioned

✅ Correct Answer: 2

Conductivity of the metal is

1. 4.382 × 10 5 S/m
2. 43.82 × 10 5 S/m
3. 438.2 × 10 5 S/m
4. .4382 × 10 5 S/m

✅ Correct Answer: 1

Current density for the field applied in question 4 would be

1. 3.15 × 10 10 A / m 3
2. 3.15 × 10 11 A / m 3
3. .315 × 10 10 A / m 3
4. 3.15 × 10 10 A / m 3

✅ Correct Answer: 2

An electron in conduction band

1. Is located near the top of the crystal
2. Is bound to its parent atom
3. Has no charge
4. Has a higher energy than an electron in the valence band

✅ Correct Answer: 4

At zero K (or at absolute zero) the conduction band may be partially filled in

1. Conductors only
2. Insulators only
3. Semiconductors only
4. Conductors and semiconductors

✅ Correct Answer: 1

Good conductors does not have hole current because they are

1. Full of electrons
2. Have large forbidden energy gap
3. Have no valence band
4. Have overlapping valence band and conduction band

✅ Correct Answer: 4

A p-type semiconductor has an acceptor density of 1020 atoms/m3 and intrinsic concentration of 2.5×1019 m-1 at 300K. The electron concentration in this p-type semiconductor is

1. 6.23 × 10 18
2. 6.25 × 10 19
3. 62.5 × 10 19
4. 62.5 × 10 18

✅ Correct Answer: 1