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Q. No.In a semiconductor,
(a)
there are no free electrons at \(0~\text{K}.\)
(b)
there are no free electrons at any temperature.
(c)
the number of free electrons increases with temperature.
(d)
the number of free electrons is less than that in a conductor.
Choose the correct option:
1. (a), (b)
2. (b), (c)
3. (a), (c), (d)
4. (a), (b), (d)
Subtopic: Â Energy Band theory |
 89%
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When an impurity is doped into an intrinsic semiconductor, the conductivity of the semiconductor,
1. increases
2. decreases
3. remains the same
4. becomes zero
Subtopic: Â Types of Semiconductors |
 85%
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A \(\mathrm{p}\text-\)type semiconductor is:
| 1. | positively charged |
| 2. | negatively charged |
| 3. | uncharged |
| 4. | uncharged at \(0~\text{K}\) but charged at higher temperatures |
Subtopic: Â Types of Semiconductors |
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Let \(n_{p}\) and \(n_{e}\) be the number of holes and conduction electrons in an intrinsic semiconductor. Then:
1. \(n_{p}> n_{e}\)
2. \(n_{p}= n_{e}\)
3. \(n_{p}< n_{e}\)
4. \(n_{p}\neq n_{e}\)
Subtopic: Â Types of Semiconductors |
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The peak voltage in the output of a half-wave rectifier is \(30 ~\text{V}.\) The rms voltage of the output wave is: (assuming no distortion in wave)
1. \(\frac{30}{\sqrt2}~\text{V}\)
2. \(15 ~\text{V}\)
3. \(\frac{15}{\sqrt2}~\text{V}\)
4. \(10 ~\text{V}\)
1. \(\frac{30}{\sqrt2}~\text{V}\)
2. \(15 ~\text{V}\)
3. \(\frac{15}{\sqrt2}~\text{V}\)
4. \(10 ~\text{V}\)
Subtopic: Â Rectifier |
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Assume that the threshold voltage of a diode is \(0.7\) V, and the forward resistance is negligible.
The current through the circuit is:
1. \(40\) mA
2. \(54\) mA
3. \(33\) mA
4. \(26\) mA
The current through the circuit is:
1. \(40\) mA
2. \(54\) mA
3. \(33\) mA
4. \(26\) mA
Subtopic: Â PN junction |
 54%
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The band gap between the valence band and the conduction band in a certain material is \(3\) eV. What is the longest wavelength of light that can create an electron-hole pair in the material, with the electron in the conduction band and the hole in the valence band? (Take \(hc\) =\(1240\) eV-nm.)
| 1. | \(414\) nm | 2. | \(300\) nm |
| 3. | \(830\) nm | 4. | \(207\) nm |
Subtopic: Â Energy Band theory |
 87%
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A \(\mathrm{p\text-n}\) junction has an electric field of \(6\times 10^{5}\) V/m in the junction and the junction width is \(500\) nm. The height of the potential barrier is:
1. \(0.6\) V
2. \(0.3\) V
3. \(0.5\) V
4. \(0.25\) V
1. \(0.6\) V
2. \(0.3\) V
3. \(0.5\) V
4. \(0.25\) V
Subtopic: Â PN junction |
 91%
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The current-voltage characteristic of an ideal \(\mathrm{p \text{-}n}\) junction diode is given by the graph as shown in the following figure:
This diode is connected with a resistance of \(5~\Omega\) in series with it as shown below:
Which of the following shows the dependence of the voltage \(V_{AB}\) and the current \(i\), when the diode is forward-biased? (\(V_{AB}\) in volt, \(i\) in ampere)
This diode is connected with a resistance of \(5~\Omega\) in series with it as shown below:
Which of the following shows the dependence of the voltage \(V_{AB}\) and the current \(i\), when the diode is forward-biased? (\(V_{AB}\) in volt, \(i\) in ampere)
| 1. | \(V_{A B}=i\cdot5+0.6\) |
| 2. | \(V_{A B}=i\cdot5-0.6\) |
| 3. | \(V_{A B}=i\cdot5+(0.6-5)\) |
| 4. | \(V_{A B}=i\cdot5+\left(0.6+5\right)\) |
Subtopic: Â PN junction |
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The voltage \(V_{AB}=20~V\) at its peak value, and is sinusoidal in time. The current \(i\) (in amperes), when plotted as a function of time, is given by:
(Consider the diodes as ideal.)
(Consider the diodes as ideal.)
| 1. |  |
2. |  |
| 3. |  |
4. |  |
Subtopic: Â PN junction |
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