Electronic Devices - Online Test
Q1. The conductivity of P – type semiconductor is due to
Answer : Option A
Explaination / Solution:
No Explaination.
Q2. An N-type Ge is obtained on doping the Ge- crystal with
Answer : Option C
Explaination / Solution:
The addition of pentavalent impurities such as antimony, arsenic or phosphorous contributes free electrons, greatly increasing the conductivity of the intrinsic semiconductor.
Q3.
A P– type crystal is obtained by doping
A) silicon with arsenic,
B) silicon with aluminum,
C) Ge with boron,
D) Ge with phosphorus.
Answer : Option A
Explaination / Solution:
Doping means the introduction of impurities into a semiconductor crystal to the defined modification of conductivity.
In P-Type Semiconductor, The addition of trivalent impurities such as boron, aluminum or gallium to an intrinsic semiconductor creates deficiencies of valence electrons,called "holes".
Q4. Majority current carriers in N – types are
Answer : Option D
Explaination / Solution:
The more abundant charge carriers are called majority carriers, which are primarily responsible for current transport in a piece of semiconductor. In n-type semiconductors they are electrons, while in p-type semiconductors they are holes.
Q5. A solid having uppermost energy – band partially filled with electrons is called
Answer : Option D
Explaination / Solution:
No Explaination.
Q6. The number of valence electrons in a good conductor is generally
Answer : Option D
Explaination / Solution:
The electron theory states that all matter is composed of atoms and the atoms are composed of smaller particles called protons, electrons, and neutrons. The electrons orbit the nucleus which contains the protons and neutrons. It is the valence electrons that we are most concerned with in electricity. These are the electrons which are easiest to break loose from their parent atom. Normally, conductors have three or less valence electrons; insulators have five or more valence electrons; and semiconductors usually have four valence electrons.
Q7. Electrons are forbidden in a band (in a crystal) called the
Answer : Option A
Explaination / Solution:
A region of values of energy that electrons in an ideal crystal (without defects) cannot have. In semiconductors the forbidden band separating the valence band and the conduction band is usually considered. In this case the energy difference between the lower level (bottom) of the conduction band and the upper level (ceiling) of the valence band is called the width of the forbidden band.
Q8. The behavior of Ge as a semi – conductor is due to the width of
Answer : Option B
Explaination / Solution:
No Explaination.
Q9. P-N junction can be used as
Answer : Option A
Explaination / Solution:
The resistance of p-n junction diode becomes low when forward biased and becomes high when reverse biased. Therefore it allows the current to pass through it when it is forward biased and does not allow when reverse biased. Hence it can rectify AC into DC.
Q10. To provide the abundance of holes the impurity added should be
Answer : Option C
Explaination / Solution:
If We introduce a "Trivalent" (3-electron) impurity into the crystalline structure, such as Aluminium, Boron or Indium, which have only three valence electrons available in their outermost orbital, the fourth closed bond cannot be formed. Therefore, a complete connection is not possible, giving the semiconductor material an abundance of positively charged carriers known as "holes" in the structure of the crystal where electrons are effectively missing
