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## Thursday, 28 January 2021

### CBSE Class 12 Physics - MCQ and Online Tests - Unit 14 - Semiconductor Electronics: Materials, Devices and Simple Circuits

#### CBSE Class 12 Physics – MCQ and Online Tests – Unit 14 – Semiconductor Electronics: Materials, Devices and Simple Circuits

Every year CBSE conducts board exams for 12th standard. These exams are very competitive to all the students. So our website provides online tests for all the 12th subjects. These tests are also very effective and useful for those who preparing for competitive exams like NEET, JEE, CA etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE Class 12 syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

#### CBSE Class 12 Physics – MCQ and Online Tests – Unit 14 – Semiconductor Electronics: Materials, Devices and Simple Circuits

Question 1.
Main function of a transistor is to :
(a) rectify
(b) simplify
(c) amplify
(d) all the above

Question 2.
To obtain p-type silicon semiconductor, we need to dope pure silicon with:
(a) aluminium
(b) phosphorus
(c) oxygen
(d)germanium

Question 3.
In intrinsic semiconductor at room temperature, the number of electrons and holes are:
(a) equal
(b) unequal
(c) infinite
(d) zero

Question 4.
On applying reverse bias to a junction diode, it:
(a) lowers the potential barrier
(b) raise the potential barrier
(c) increases the majority carrier current
(d) increases the minority carrier current

Answer: (b) raise the potential barrier

Question 5.
With fall of temperature, the forbidden energy gap of a semiconductor
(a) increases
(b) decreases
(c) sometimes increases and sometimes decreases
(d) remains unchanged

Question 6.
For germanium crystal, the forbidden energy gap in joules
(a) 1.216 × 10-19
(b) 1.76 × 10-19
(c) 1.6 × 10-19
(d) zero

Question 7.
Number of electrons in the valence shell of a semiconductor is:
(a) 1
(b) 2
(c) 3
(d) 4

Question 8.
To obtain electrons as majority charge carriers in a semiconductors the impurity mixed is:
(a) monovalent
(b) divalent
(c) trivalent
(d) pentavalent

Question 9.
In the middle of the depletion layer of a reverse biased p-n junction, the:
(a) electric field is zero
(b) potential is maximum
(c) electric field is maximum
(d) potential zero.

Question 10.
Bonds in a semiconductor :
(a) trivalent
(b) covalent
(c) bivalent
(d) monovalent

Question 11.
In a common base amplifier the phase difference between the input signal voltage and output voltage is :
(a) π/2
(b) 0
(c) π/4
(d) π

Question 12.
Energy bands in solids are a consequence of:
(a) Ohm’s Law
(b) Pauli’s exclusion principle
(c) Bohr’s theory
(d) Heisenberg’s uncertainty principle

Question 13.
Semiconductors of both p-type and n-type are produced by:
(a) ionic solids
(b) covalent solids
(c) metallic solids
(d) molecular solids

Question 14.
In semi conductor which are responsible for conduction:
(a) only electron
(b) electron and hole both
(c) only hole
(d) None of these

Answer: (b) electron and hole both

Question 15.
In a p-type semiconductor, current conduction is by:
(a) atoms
(b) holes
(c) electrons
(d) protons

Question 16.
In binary system III represents:
(a) 1
(b) 3
(c) 7
(d) 100

Question 17.
On heating, resistance of semiconductors:
(a) decreases
(b) increases
(c) remains same
(d) first increases then decreases

Question 18.
The relation between number of free electrons (n) in a semiconductor and temperature (T) is given by:
(a) n ∝ T
(b) n ∝ T²
(c) n ∝ T1/2
(d) n ∝ T3/2

Question 19.
p-n junction diode can be used as:
(a) amplifier
(b) oscillator
(c) detector
(d) modulator

Question 20.
In reverse biasing:
(a) large amount of current flows
(b) no current flows
(c) potential barrier across junction increases
(d) depletion layer resistance increases

Answer: (c) potential barrier across junction increases

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