\(\mathrm{C}\), \(\mathrm{Si}\), and \(\mathrm{Ge}\) have the same lattice structure. Why is the \(\mathrm{C}\) insulator?

1. because ionization energy for \(\mathrm{C}\) is the least in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\).
2. because ionization energy for \(\mathrm{C}\) is highest in comparison to \(\mathrm{Si}\) and \(\mathrm{Ge}\).
3. the number of free electrons for conduction in \(\mathrm{Ge}\) and \(\mathrm{Si}\) is significant but negligibly small for \(\mathrm{C}\).
4. both (2) and (3).

Subtopic:  Energy Band theory |
 71%
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Suppose a pure Si crystal has \(5\times10^{28}~\text{atoms m}^{-3}\)It is doped by a \(1\) ppm concentration of pentavalent As. The number of electrons and holes are, respectively: (Given: \(n_i=1.5\times10^{16}~\text{m}^{-3}\))

1. \(5\times10^{22}~\text{m}^{-3}, 4.5\times10^{9}~\text{m}^{-3}\) 
2. \(4.5\times10^{9}~\text{m}^{-3}, 5\times 10^{22}~\text{m}^{-3}\) 
3. \(5\times10^{22}~\text{m}^{-3}, 5\times10^{22}~\text{m}^{-3}\)
4. \(4.5\times10^{9}~\text{m}^{-3}, 4.5\times 10^{9}~\text{m}^{-3}\)
Subtopic:  Types of Semiconductors |
 55%
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Why can't we take one slab of p-type semiconductor and physically join it to another slab of n-type semiconductor to get a p-n junction?

1. the diffusion of majority charge carriers will not occur.
2. the junction will behave as a discontinuity for the flowing charge carriers.
3. the junction will behave as a continuity for the flowing charge carriers.
4. both (1) and (2).

Subtopic:  PN junction |
 77%
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The V-I characteristic of a silicon diode is shown in the figure. The resistance of the diode at ID=15 mA is: 

 

1. 20 Ω
2. 30 Ω
3. 15 Ω
4. 10 Ω

Subtopic:  PN junction |
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The \((V-I)\) characteristic of a silicon diode is shown in the figure. The resistance of the diode at \(V_D=-10\) V is:

     
1. \(1\times10^7~\Omega~\)
2. \(2\times10^7~\Omega~\)
3. \(3\times10^7~\Omega~\)
4. \(4\times10^7~\Omega~\)

Subtopic:  PN junction |
 77%
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In a Zener regulated power supply, a Zener diode with \(V_Z=6~\text{V}\)  is used for regulation. The load current is to be \(4.0~\text{mA}\) and the unregulated input is \(10.0~\text{V}\). The value of the series resistor \(R_S\) will be:\((\text{Assume }I_Z=5I_L)\)
1. less  than \(100~\Omega\)
2. zero
3. infinite
4. \(150~\Omega\)
Subtopic:  Applications of PN junction |
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Which one of the following is not true for the photodiodes?

1. The current in the forward bias is more than the current in the reverse bias.
2. Photodiodes are preferably used in the reverse bias condition for measuring light intensity.
3. Photodiodes are preferably used in the forward bias condition for measuring light intensity
4. In photodiodes, only a small portion of the incident photons gets converted to electric current.

Subtopic:  Applications of PN junction |
 61%
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Which material is preferred for solar cells?
1. Si
2. GaAs
3. CdS
4. both Si and GaAs

Subtopic:  Applications of PN junction |
 59%
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The output waveform (Y) of the AND gate for the following inputs A and B given in the figure is:

    

1.
2.
3.
4. None of these
Subtopic:  Logic gates |
 75%
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The output waveform (\(\text{Y}\)) of the \(\mathrm{OR}\) gate for the following inputs \(\mathrm{A}\) and\(​​​​\mathrm{B}\) given in the figure is:

 
 

1.
2.
3.
4. none of these
Subtopic:  Logic gates |
 79%
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