Semiconductor Electronics: Materials, Devices and Simple Circuits Test 49

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 49

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Question 1
1 / -0

Which of the following statements is true for a p-n-p transistor when used in an amplifier circuit ?

A
Emitter is connected to negative terminal of a battery.

B
Base current is always lower than emitter current.

C
Collector is connected to positive terminal of a battery

D
Collector current is always more than the emitter current

Solution

If a p-n-p transistor is to be used as an amplifier in common emitter mode, base-emitter must be biased forward. So, base should be connected with the positive terminal of the battery whereas emitter should be connected with the negative terminal of the battery.
Question 2
1 / -0

The combination of gates shown below yields.

A
NAND gate.

B
NOR gate.

C
XOR gate.

D
OR gate.

Solution

NAND gate.
Put A as 1 and B as 0
then
A as 0 and B as 1
Question 3
1 / -0

The relation between dynamic plate resistance $$\left( r _ { p } \right)$$ of a vacuum diode and plate current in the space charge limited region, is

A
$$r _ { p } \propto I _ { p }$$

B
$$r _ { p } \propto I _ { p } ^ { 3 / 2 }$$

C
$$r _ { p } \propto \dfrac { 1 } { I _ { p } }$$

D
$$r _ { p } \propto \dfrac { 1 } { \left( I _ { p } \right) ^ { 1 / 3 } }$$

Solution

The dynamic plate resistance is $$r_p=\dfrac{\Delta V_p}{\Delta i_p}$$
Now for a vacuum diode $$i_p=K_p^{-3/2} \Rightarrow =V_p= \left(\dfrac{i_p}{K} \right)^{2/3}$$

$$\Rightarrow \dfrac{\Delta V_p}{\Delta i_p} =\dfrac{2}{3 K^{2/3}} \times \dfrac{1}{i_p^{\left(\dfrac{2}{3}-1 \right)}}$$

$$\Rightarrow r_p=(constant) I_p^{-1/3} \Rightarrow r _ { p } \propto \dfrac { 1 } { \left( I _ { p } \right) ^ { 1 / 3 } }$$
Question 4
1 / -0

A gate in which all the inputs must be low to get a high output is called

A
NAND gate

B
An inverter

C
NOR gate

D
AND gate

Solution

A gate in which all the inputs must be low to get a high output is called a nor gate.
Question 5
1 / -0

The input signals at NAND gate is given below

A

B

C

D

Solution
Question 6
1 / -0

The given figure shows the waveforms for three inputs $$A,B $$ and $$C$$ and that for the output $$Y$$ of a logic circuit. The logic circuit is

A
$$XOR$$ Gate

B
$$XNOR$$ Gate

C
$$NAND$$ Gate

D
$$NOR$$ Gate
Question 7
1 / -0

In a P-N junction, a potential barrier exists across the function. A hole with kinetic energy of 300 meV *approaches the junction Find the kinetic energy of the hole it crosses the junction it the hole approached the Junction from the p-side and

A
105 me V

B
55 me V

C
50 me V

D
100 me V

Solution

Potential barrier 'd'$$=250$$mev
Initial KE of hole$$=300$$mev
KE of the hole decreases when the junction in forward biased and increases when reverse biases in given Px dioide.
(a) Final KE$$=(300-250)$$ mev$$=50$$ mev
(b) Initial KE$$=(300+250)$$ mev$$=550$$ mev.
Question 8
1 / -0

The magnitude of the force between a pair of conductors, each of length 110 cm, carrying a current of 10 A and separated by a distance of 10 cm is

A
$$55 \times 10 ^ { - 5 } N$$

B
$$44 \times 10 ^ { - 5 } N$$

C
$$33 \times 10 ^ { - 5 } N$$

D
$$22 \times 10 ^ { - 5 } N$$

Solution

$$\begin{array}{l} B=\frac { { { \mu _{ o } }i } }{ { 2\pi r } } \\ F=\frac { { { \mu _{ o } }i } }{ { 2\pi r } } \times iL \\ =\frac { { 4\pi \times { { 10 }^{ -7 } }\times 10\times 10\times 110 } }{ { 2\pi .10 } } \\ =22\times { 10^{ -5 } } \\ =2.2\times { 10^{ -4 } }N \\ Hence, \\ option\, \, D\, \, is\, \, correct\, \, answer. \end{array}$$
Question 9
1 / -0

A wire of resistance 'R' is cut into four equal parts and they are bundled together side by side to form a thicker wire. The resistance of the bundle is

A
$$\cfrac{R}{16}$$

B
$$\cfrac{R}{2}$$

C
$$2R$$

D
$$4R$$

Solution
Question 10
1 / -0

With the rise of temperature, the specific resistance of semiconductor?

A
Increases

B
Remains unchanged

C
Decreases

D
None of these

Solution