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 |
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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
Subtopic: Â PN junction |
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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)

 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.)
 1 2 3 4

Subtopic: Â PN junction |
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The circuit shown in figure is given an input signal $$V_i,$$ which varies with time and the corresponding output is $$V_o.$$ Then,

 1 $$V_o=V_i+E$$ 2 $$V_o=V_i-E$$ 3 $$V_o=V_i,$$  only when $$V_i>E$$ 4 $$V_o=V_i,$$ only when $$V_i Subtopic: Â PN junction | From NCERT Please attempt this question first. Hints Please attempt this question first. The resistance between \(A$$ and $$B$$ is

 1 $$100~\Omega$$ if $$V_A>V_B$$ and $$200~\Omega$$ if $$V_AV_B$$ 3 $$100~\Omega$$ 4 $$200~\Omega$$
Subtopic: Â PN junction |
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In half-wave rectification, if the input frequency is $$60$$ Hz, then the output frequency would be:
1. $$120$$ Hz
2. zero
3. $$30$$ Hz
4. $$60$$ Hz
Subtopic: Â Rectifier |
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As the temperature increases, the electrical resistance:
 1 decreases for conductors but increases for semiconductors. 2 increases for both conductors and semiconductors. 3 decreases for both conductors and semiconductors. 4 increases for conductors but decreases for semiconductors.
Subtopic: Â Energy Band theory |
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In the given circuits (a), (b) and (c), the potential drop across the two $${\mathrm{p\text-n}}$$ junctions are equal in:

 1 both circuits (a) and (c) 2 circuit (a) only 3 circuit (b) only 4 circuit (c) only
Subtopic: Â PN junction |
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In the circuit shown in the figure, $$V_A>V_B.$$ Which of the diodes conduct?

 1 only $$D_3$$ 2 $$D_1$$ and $$D_3$$ 3 all of the diodes 4 none of the diodes
Subtopic: Â PN junction |
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