Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy gaps represented by \(\left(E_g\right)_C,(E_g)_{Si}~\text{and}~(E_g)_{Ge}\) respectively. Which one of the following relationships is true in their case?

1. \(\left(E_g\right)_C<\left(E_g\right)_{G e} \) 2. \(\left(E_g\right)_C>\left(E_g\right)_{S i} \)
3. \(\left(E_g\right)_C=\left(E_g\right)_{S i} \) 4. \(\left(E_g\right)_C<\left(E_g\right)_{S i}\)

Subtopic:  Energy Band theory |
 70%
From NCERT
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In the given figure, the potential difference between A and B is:

1. 0 2. 5 volt
3. 10 volt 4. 15 volt
Subtopic:  PN junction |
 56%
From NCERT
PMT - 2000
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A semiconductor is known to have an electron concentration of 8×1013 cm-3 and a hole concentration of 5×102 cm-3. The semiconductor is:

1.  n-type

2.  p-type

3.  intrinsic

4.  insulator

Subtopic:  Types of Semiconductors |
 87%
From NCERT
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When a p-n junction is forward biased, then:

1. the depletion region becomes thick.
2. the p-side is at a higher potential than n side.
3. the current flowing is zero.
4. the effective resistance is of the order of \(10^6 ~\Omega\).

Subtopic:  PN junction |
 83%
From NCERT
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If a small amount of aluminium is added to the silicon crystal:

1. its resistance decreases.
2. it becomes a p-type semiconductor.
3. there will be fewer free electrons than holes in the semiconductor.
4. All of these are correct.
Subtopic:  Types of Semiconductors |
 75%
From NCERT
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If in a p-n junction, a square input signal of 10 V is applied as shown, then the output across RL will be:
              

1. 2.
3. 4.
Subtopic:  Rectifier |
 66%
From NCERT
NEET - 2015
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The given graph represents the V-I characteristic for a semiconductor device. Which of the following statement is correct?

1. It is a V-I characteristic for a solar cell where point A represents open-circuit voltage and point B represents short-circuit current.
2. It is for a solar cell and points A and B represent open-circuit voltage and current respectively.
3. It is for a photodiode and points A and B represent open-circuit voltage and current respectively.
4. It is for a LED and points A and B represent open-circuit voltage and short circuit current respectively.
Subtopic:  Applications of PN junction |
 68%
From NCERT
NEET - 2014
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Pure Si at 500 K has equal number of electron (ne) and hole (nh) concentration of 1.5×1016 m-3. Doping by indium increases nh to 4.5×1022 m-3. The doped semiconductor is of:

1. n-type with electron concentration \(n_{e}=5\times10^{22}~m^{-3}\)
2. p-type with electron concentration \(n_{e}=2.5\times10^{23}~m^{-3}\)
3. n-type with electron concentration \(n_{e}=2.5\times10^{10}~m^{-3}\)
4. p-type with electron concentration \(n_{e}=5\times10^{9}~m^{-3}\)
Subtopic:  Types of Semiconductors |
 69%
From NCERT
NEET - 2011
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A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit, as shown in the figure. The current through the diode is:

                      

1. 10 mA

2. 15 mA

3. 20 mA

4. 5 mA

Subtopic:  Applications of PN junction |
 60%
From NCERT
NEET - 2011
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In a PN-junction diode:

1. the current in the reverse biased condition is generally very small.
2. the current in the reverse biased condition is small but the forward-biased current is independent of the bias voltage.
3. the reverse-biased current is strongly dependent on the applied bias voltage.
4. the forward-biased current is very small in comparison to reverse-biased current.
Subtopic:  PN junction |
 67%
From NCERT
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