The band gap between the valence band and the conduction band in a certain material is \(3~\text{eV}.\) 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 \(hc=1240~\text{eV-nm}\) )
1. \(414~\text{nm}\)
2. \(300~\text{nm}\)
3. \(830~\text{nm}\)
4. \(207~\text{nm}\)

Subtopic:  Energy Band theory |
 88%
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A \(\mathrm{p\text-n}\) junction has an electric field of \(6\times 10^{5}~\text{V/m}\) in the junction and the junction width is \(500~\text{nm}.\) The height of the potential barrier is:
1. \(0.6~\text V\) 
2. \(0.3~\text V\) 
3. \(0.5~\text V\) 
4. \(0.25~\text V\) 
Subtopic:  PN junction |
 89%
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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:  PN junction |
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The voltage \(V_{AB}=20~\text{V}\) 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:  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 \(V_i<E\)
Subtopic:  PN junction |
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The resistance between \(A\) and \(B\) is
           
1. \(100~\Omega\) if \(V_A>V_B\) and \(200~\Omega\) if \(V_A<V_B\)
2. \(100~\Omega\) if \(V_A<V_B\) and \(200~\Omega\) if \(V_A>V_B\)
3. \(100~\Omega\)
4. \(200~\Omega\)
Subtopic:  PN junction |
 75%
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In half-wave rectification, if the input frequency is \(60\) Hz, the output frequency will be:
1. \(120\) Hz 2. zero
3. \(30\) Hz 4. \(60\) Hz
Subtopic:  Rectifier |
 68%
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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:  Energy Band theory |
 75%
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In the given circuits \((a),\) \((b),\) and \((c),\) the potential drop across the two \({\mathrm{p\text-n}}\) junctions is equal in:

            
1. both circuits \((a)\) and \((c)\)
2. circuit \((a)\) only
3. circuit \((b)\) only
4. circuit \((c)\) only
Subtopic:  PN junction |
 65%
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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:  PN junction |
 53%
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