$$\mathrm{C}$$, $$\mathrm{Si}$$, 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 |
73%
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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 |
58%
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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  is:

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

1. $$1\times10^7~\Omega~$$
2. $$2\times10^7~\Omega~$$
3. $$3\times10^7~\Omega~$$
4. $$4\times10^7~\Omega~$$

Subtopic:  PN junction |
80%
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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 |
62%
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Which material is preferred for solar cells?
1. $$\text{Si}$$
2. $$\text{GaAs}$$
3. $$\text{CdS}$$
4. both $$\text{Si}$$ and $$\text{GaAs}$$

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 |
76%
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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 |
80%
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