131. The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $$2480\,nm$$ is incident on it. The band gap in $$\left( {eV} \right)$$ for the semiconductor is
A
$$2.5\,eV$$
B
$$1.1\,eV$$
C
$$0.7\,eV$$
D
$$0.5\,eV$$
Answer :
$$0.5\,eV$$
132.
Which of the following gates corresponds to the truth table given below?
| Inputs | Output | |
|---|---|---|
| A | B | Y |
| 1 | 1 | 0 |
| 1 | 0 | 1 |
| 0 | 1 | 1 |
| 0 | 0 | 1 |
A
NAND
B
OR
C
AND
D
XOR
Answer :
NAND
133.
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
A
$$p$$-type semiconductor
B
insulator
C
metal
D
$$n$$-type semiconductor
Answer :
$$p$$-type semiconductor
134. If a small amount of antimony is added to germanium crystal
A
the antimony becomes an acceptor atom
B
there will be more free electrons than holes in the semiconductor
C
its resistance is increased
D
it becomes a $$p$$-type semiconductor
Answer :
there will be more free electrons than holes in the semiconductor
135.
Symbolic representation of four logic gates are shown as
Pick out which ones are for AND, NAND and NOT gates, respectively.
A
(iii), (ii) and (i)
B
(iii), (ii) and (iv)
C
(ii), (iv) and (iii)
D
(ii), (iii) and (iv)
Answer :
(ii), (iv) and (iii)
136. The current voltage relation of a diode is given by $$I = \left( {{e^{1000V/T}} - 1} \right)mA,$$ where the applied voltage $$V$$ is in volts and the temperature $$T$$ is in degree kelvin. If a student makes an error measuring $$ \pm 0.01\,V$$ while measuring the current of $$5\,mA$$ at $$300\,K,$$ what will be the error in the value of current in $$mA$$ ?
A
$$0.2\,mA$$
B
$$0.02\,mA$$
C
$$0.5\,mA$$
D
$$0.05\,mA$$
Answer :
$$0.2\,mA$$
137. The plate resistance of a triode is $$3 \times {10^3}ohms$$ and its mutual conductance is $$1.5 \times {10^{ - 3}}amp/volt.$$ The amplification factor of the triode is
A
$$5 \times {10^{ - 5}}$$
B
4.5
C
45
D
$$2 \times {10^5}$$
Answer :
4.5
138. A working transistor with its three legs marked $$P, Q$$ and $$R$$ is tested using a multimeter. No conduction is found between $$P$$ and $$Q.$$ By connecting the common (negative) terminal of the multimeter to $$R$$ and the other (positive) terminal to $$P$$ or $$Q,$$ some resistance is seen on the multimeter. Which of the following is true for the transistor?
A
It is an npn transistor with $$R$$ as base
B
It is a pnp transistor with $$R$$ as collector
C
It is a pnp transistor with $$R$$ as emitter
D
It is an npn transistor with $$R$$ as collector
Answer :
It is an npn transistor with $$R$$ as base
139. In a triode, $${g_m} = 2 \times {10^{ - 3}}oh{m^{ - 1}};\mu = 42;$$ resistance of load, $$R = 50\,kilo\,ohm.$$ The voltage amplification obtained from this triode will be
A
30.42
B
29.57
C
28.18
D
27.15
Answer :
29.57
140.
This question has Statement - 1 and Statement - 2. Of the
four choices given after the statements, choose the one
that best describes the two statements.
Statement - 1 : Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement - 2 : The state of ionosphere varies from hour to hour, day to day and season to season.
A
Statement - 1 is true, Statement - 2 is true, Statement - 2 is the correct explanation of Statement - 1.
B
Statement - 1 is true, Statement - 2 is true, Statement - 2 is not the correct explanation of Statement - 1.
C
Statement - 1 is false, Statement - 2 is true.
D
Statement - 1 is true, Statement - 2 is false.
Answer :
Statement - 1 is true, Statement - 2 is true, Statement - 2 is not the correct explanation of Statement - 1.