Semiconductor Electronics: Materials, Devices and Simple Circuits Test 46

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 46

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Weekly Quiz Competition

Question 1
1 / -0

If a p-n junction diode is reverse biased, then the resistance measure by an ohm-meter will be

A
zero

B
low

C
high

D
infinite

Solution

A p-n junction diode conducts negligible (not zero) current under reverse biased mode,

Hence there's high resistance is offered under reverse bias mode.

Option $$\textbf C$$ is correct.
Question 2
1 / -0

In an unbiased PN-junction,

A

The junction current at equilibrium is zero as charges do not cross the junction

B
The junction current reduces with rise in temperature

C
The junction current at equilibrium is zero as equal but opposite carriers are crossing the junction

D
The junction current is due to minority carriers only

Solution
Question 3
1 / -0

In the case of forward biasing of a p-n junction diode,which one of the following figure correctly depicts the direction of conventional current?

A

B

C

D

Solution

In this case,on the p-side majority charge carrier are holes which move towards the negative terminal of the battery and on the n-side majority charge carriers are electrons which move towards the positive terminal of the battery.
Therefore option c is correct.
Question 4
1 / -0

A Zener diode is connected to a battery and a load as shown below: The current $$I,I_{Z}$$ and $$I_{L}$$ are respectively :

A
$$12.5\ mA,735\ mA,5\ mA$$

B
$$12.5\ mA,5\ mA,7.5\ mA$$

C
$$15\ mA,7.5\ mA,7.5\ mA$$

D
$$15\ mA,5\ mA,10\ mA$$

Solution

Given that,

$$ {{R}_{L}}=2\,k\Omega $$

$$ R=4\,k\Omega $$

$$ V=60\,V $$

$$ {{V}_{Z}}=10\,V $$

The Zener diode in the breakdown region maintain a constant voltage, the voltage across $$R_{L}$$ is

$${V_{{R}_{L}}}={{V}_{L}}=10\,V$$

Now, the load current is

$$ {{I}_{L}}=\dfrac{{{V}_{L}}}{{{R}_{L}}} $$

$$ {{I}_{L}}=\dfrac{10}{2000} $$

$$ {{I}_{L}}=5\,mA $$

Now, using Kirchhoff’s law

$$ {{I}_{L}}{{R}_{L}}-60+4000\Omega I=0 $$

$$ 10-60+4000I=0 $$

$$ 4000I=50 $$

$$ I=\dfrac{50}{4000} $$

$$ I=0.0125 $$

$$ I=12.5\,mA $$

Now, from Kirchhoff’s current law

$$ I={{I}_{Z}}+{{I}_{L}} $$

$$ {{I}_{Z}}=12.5-5 $$

$$ {{I}_{Z}}=7.5\,mA $$

Hence, the current is $$12.5\ mA$$, $$5\ mA$$ and $$7.5\ mA$$
Question 5
1 / -0

The following combination of gates is equivalent to :

A

B

C

D

Solution

The correct option is B.
Question 6
1 / -0

For a purely resistive circuit, which of the following statements is incorrect?

A
rms current will vary if the frequency of the source is varied

B
Power factor is equal to $$1$$

C
Current and voltage are in phase

D
The average Power dissipated through the resistor is directly proportional to $${i}_{rms}^{2}$$

Solution
Question 7
1 / -0

Which is not true:

A
Resistance of metals increases with increasing temperature

B
Resistance of semi-conductors decreases with rise of temperature

C
Resistance of an electrolyte increases with rise of temperature

D
None of the above

Solution

(A) We know in metals the atoms are closely packed thus increasing temperature increases the energy of the molecules present in the metal, which leads to vigorous vibration of the molecules resulting in violent collision of the electrons with each other and hence increasing the resistance of the metal.
(B) When we increase temperature in semi-conductors the electrons in the valence gets excited and jumps into the conductance band thus increasing the conductance.As conductance increases,resistance decreases.
(C) Resistance offered in an electrolyte is due to the limited mobility of ions which,in an electrolyte current is carried by moving ions. And we know ion mobility increases with temperature,hence decreasing the resistance of electrolytes with increasing temperature.
Question 8
1 / -0

Select the correct statement from the following

A
a diode can be used as a rectifier

B
a diode cannot be used as a rectifier

C
the current in a diode is always proportional to the applied voltage

D
None of these

Solution
Question 9
1 / -0

The combination of the gates shown will produce

A
AND gate

B
NAND gate

C
NOR gate

D
XOR gate

Solution
Question 10
1 / -0

In the circuit given the current through the Zener diode is :- -

A
$$10 \mathrm { mA }$$

B
$$6.67 \mathrm { mA }$$

C
$$5 \mathrm { mA }$$

D
$$3.33 \mathrm { mA }$$