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In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is a/an: 
      

1. \(\mathrm{p}\text-\)type semiconductor
2. insulator
3. metal
4. \(\mathrm{n}\text-\)type semiconductor
Subtopic:  Energy Band theory |
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Level 2: 60%+
AIPMT - 2007
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Identify the incorrect statement from the following:
1. The resistivity of a semiconductor increases with an increase in temperature.
2. Substances with an energy gap of the order of \(10~\text{eV}\) are insulators.
3. In conductors, the valence and conduction bands may overlap.
4. The conductivity of a semiconductor increases with an increase in temperature.
Subtopic:  Energy Band theory |
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Level 1: 80%+
AIPMT - 2005
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Carbon, Silicon, and Germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy gaps represented by \(\left(E_g\right)_C,(E_g)_{Si}~\text{and}~(E_g)_{Ge}\) respectively. Which one of the following relationships is true in their case?
1. \(\left(E_g\right)_C<\left(E_g\right)_{G e} \)
2. \(\left(E_g\right)_C>\left(E_g\right)_{S i} \)
3. \(\left(E_g\right)_C=\left(E_g\right)_{S i} \)
4. \(\left(E_g\right)_C<\left(E_g\right)_{S i}\)

Subtopic:  Energy Band theory |
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Level 2: 60%+
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\(\mathrm{p\text-n}\) photodiode is fabricated from a semiconductor with a band gap of \(2.5~\text{eV}.\) It can detect a signal of wavelength:
1. \(6000~\mathring{A}\)
2. \(4000~\text{nm}\)
3. \(6000~\text{nm}\)
4. \(4000~\mathring{A}\)  
Subtopic:  Energy Band theory |
 64%
Level 2: 60%+
AIPMT - 2009
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A semiconductor is known to have an electron concentration of \(8\times 10^{13}~\text{cm}^{-3},\) and a hole concentration of \(5\times 10^{2}~\text{cm}^{-3}.\) The semiconductor is:

1. \(\mathrm{n}\text-\)type 2. \(\mathrm{p}\text-\)type
3. intrinsic 4. insulator
Subtopic:  Types of Semiconductors |
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\(\mathrm{C}\) and \(\mathrm{Si}\) both have the same lattice structure, having \(4\) bonding electrons in each. However, \(\mathrm{C}\) is an insulator whereas \(\mathrm{Si}\) is an intrinsic semiconductor. This is because:
1. in the case of \(\mathrm{C},\) the valence band is not completely filled at absolute zero temperature.
2. in the case of \(\mathrm{C},\) the conduction band is partly filled even at absolute zero temperature.
3. the four bonding electrons in the case of \(\mathrm{C}\) lie in the second orbit, whereas in the case of \(\mathrm{Si},\) they lie in the third.
4. the four bonding electrons in the case of \(\mathrm{C}\) lie in the third orbit, whereas for \(\mathrm{Si},\) they lie in the fourth orbit.
Subtopic:  Energy Band theory |
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NEET - 2012
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Pure \(\mathrm{Si}\) at \(500~\text K\)  has an equal number of electrons \((n_i)\) and the hole \((n_h)\) concentration of \(1.5\times10^{16}~\text{m}^{-3}.\) Doping by indium increases the hole concentration \(n_h\) to \(4.5\times 10^{22}~\text{m}^{-3}.\) The doped semiconductor is of:
1. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=5\times10^{22}~\text{m}^{-3}\)
2. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=2.5\times10^{23}~\text{m}^{-3}\)
3. \(\mathrm{n}\text-\)type with electron concentration \(n_{e}=2.5\times10^{10}~\text{m}^{-3}\)
4. \(\mathrm{p}\text-\)type with electron concentration \(n_{e}=5\times10^{9}~\text{m}^{-3}\)
Subtopic:  Types of Semiconductors |
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NEET - 2011
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If the reverse bias in a junction diode is changed from \(5~\text V\) to \(15~\text V\) then the value of current changes from \(38~\mu \text{A}\) to \(88~\mu \text{A}.\) The resistance of the junction diode will be:
1. \(4\times10^{5}\) 
2. \(3\times10^{5}\)
3. \(2\times10^{5}\)
4. \(10^{6}\)

Subtopic:  PN junction |
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The given circuit has two ideal diodes connected as shown in the figure below. The current flowing through the resistance \(R_1\) will be:
       

1. \(2.5~\text A\)  2. \(10.0~\text A\) 
3. \(1.43~\text A\)  4. \(3.13~\text A\) 
Subtopic:  PN junction |
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Level 1: 80%+
NEET - 2016
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What is the reading of the ideal ammeters \(A_1\) and \(A_2\) connected in the given circuit diagram, if \(\mathrm{p\text-n}\) junction diodes are ideal?

    

1. \(2~\text A\)  and zero 2. \(3~\text A\)  and \(2~\text A\) 
3. \(2~\text A\)  and \(3~\text A\)  4. Zero and \(2~\text A\) 


 
Subtopic:  PN junction |
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