Electronics and Devices and circuits MCQ

1.Forbidden energy gap between valence band and conduction band is least in the case of

(a) mica              b) pure silicon                   (¢) pure germanium         (d) impure silicon

pure silicon

2.Temperature coefficient of resistance in a pure semiconductor is

(a) zero

(b) positive

0) negative

(d) dependent on size of specimen

 Negative

3.Forbidden energy gap in semiconductors is of the order of

(a) 7eV M             b) 1eV

(c) 0.01eV           (d) 0.05eV

1ev

4.At 0°K, the forbidden energy gap in germanium is

(a) 0.785 eV          (b) L21eV   {c. 0.72eV    (d) 1.1eV

0.785ev

5.At 300°K, the forbidden energy gap in germanium is :

(a) 0.785 eV     (b) 1.21eV

we) 0.72eV       (d) 11eV

0.72ev

6.At 0°K, the forbidden energy gap in silicon is

(a) 0.785 eV     (b) 1.21eV    (c) 0.72eV    (d) 1.1eV

1.21ev

7. A300°K, the forbidden energy gap in silicon is

(a) 0.785 eV      (b) 1.21eV    (c)  0.72eV     (d)  1.1eV

1.1ev

8.The diffusion length of a carrier depends on

(a) shape of the semiconductor         (b) life time of the carriers alone

c) mobility and life time of the carriers   (d mobility of the carriers alone

mobility and life time of the carriers

9.Donor impurity atom in a semiconductor result in new

(a) wide energy band b) narrow energy band

(c) discrete energy level just below conduction level  d) energy level just above valence level

narrow energy band

10.A germanium atom contains  ?

 (a) four valence electrons     (b) six valence electrons

 (c) four protons                   (d) six protons

A)four valence electrons

11.In Ge, an electron in the conduction band

 (a) is bound to its parent atom       b) has a higher energy than an electron in the valence band 

 (c) has zero charge                       (d) is located near the top of the crystal

B) has a higher energy than an electron in the valence band

12.In Ge, when atoms are held together by the sharing of valence electrons

 (a) each shared atom leaves a hole            (b) valence electrons are free to move away from the nucleus (c) velence electrons form irreversible covalent bands    (d) valence electrons form reversible covalent

(d) valence electrons form reversible covalent

13.A hole is the vacancy created when

 (a) a free electron moves on application of electric field

b) an electron breaks its covalent band                (c) an atomic core moves

d) an electron reverts from conduction band to valence band

b) an electron breaks its covalent band

14.n an electric field is applied to an intrinsic semiconductor at room temperature say from left

to right

a) both electrons and holes drift to the right         b) both electrons and holes drift to the left c) electrons drift to the right while the holes  drift to the left   

d)  electrons drift to the left  while the holes  drift to left

d)electrons drift to the left while the holes drift to left

15.In Ge or Si, light doping corresponds to impurity of following magnitude

(a) 1 in 10⁸

(b)1 in 10⁶

(o)1 in 10⁵ 

(d) 1 in 10

1 in 10