Semiconductor Electronics: Materials, Devices and Simple Circuits Test 55

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Semiconductor Electronics: Materials, Devices and Simple Circuits Test 55

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Weekly Quiz Competition

Question 1
1 / -0

Figure shown a DC voltage regulator circuit, with a Zener diode of breakdown voltage = $$6V$$. If the unregulated input voltage varies between $$10 V$$ to $$16 V$$, then what is the maximum Zener current ?

A
$$2.5 \, mA$$

B
$$3.5 \, mA$$

C
$$7.5 \, mA$$

D
$$1.5 \, mA$$

Solution

Maximum current will flow from zener if input voltage is maximum.
When zener diode works in breakdown state, voltage across the zener will remain same.
$$\therefore V_{across \,4k\Omega} = 6V$$

$$\therefore$$ Current through $$4K\Omega = \dfrac{6}{4000} A = \dfrac{6}{4}mA$$
since input voltage $$= 16V$$
$$\therefore$$ Potential difference across $$2K\Omega = 10V$$

$$\therefore$$ Current difference across $$2K\Omega = \dfrac{}{} = 5mA$$

$$\therefore$$ Current through zener diode
$$= (I_S - I_L) = 3.5 \,mA$$
Question 2
1 / -0

At equilibrium, in a p-n junction diode the net current is

A
due to diffusion of majority charge carriers.

B
due to drift of minority charge carriers

C
zero as diffusion and drift currents are equal and opposite.

D
zero as no charge carriers cross the junction.

Solution

At equilibrium, the p-n junction has the same number of majority and minority carriers moving in opposite directions. The net current is the sum of drift current and diffusion current. So the net current will be zero as diffusion and drift currents are equal and opposite.
Option (C) are correct.
Question 3
1 / -0

In the given circuit, diode $$D$$ is ideal. The potential difference across $$4\Omega$$ resistance is:

A
$$10\ V$$

B
$$5\ V$$

C
$$4\ V$$

D
$$none\ of\ these$$

Solution
Question 4
1 / -0

What is the plate current in a diode valve under the space charge limited operation, when the plate potential is $$60\ V$$? In a diode valve, the plate current is $$320\ mA$$, when the plate potential is $$240$$ volts:

A
$$30\ mA$$

B
$$20\ mA$$

C
$$40\ mA$$

D
$$10\ mA$$

Solution
Question 5
1 / -0

The impurity added in germanium crystal to make $$n-$$ type semi-conductor is:

A
aluminium

B
gallium

C
iridium

D
phosphorus

Solution
Question 6
1 / -0

In the given diagram, assume that diode is not ideal. The drift current for diode is $$40\mu A$$. The potential difference across the $$4\Omega$$ resistance is:

A
$$10\ V$$

B
$$40\times 10^{-6}V$$

C
$$160\times 10^{-6}\ V$$

D
$$none\ of\ these$$

Solution
Question 7
1 / -0

What is the work function of tungsten at $$1500\ K$$ temperature, when a diode valve with a tungsten filament works at $$1500\ K$$? Assume the work function of tungsten at $$0\ K$$ is $$4.52\ eV$$:

A
$$4.71\ eV$$

B
$$0.39\ eV$$

C
$$8.86\ eV$$

D
$$1.25\ eV$$

Solution
Question 8
1 / -0

In an insulator, band gap of the order of?

A
$$0.1eV$$

B
$$1eV$$

C
$$5eV$$

D
$$100eV$$

E
$$1MeV$$

Solution

In an insulator the forbidden band gap is of the order of $$5eV$$.
Question 9
1 / -0

The energy gap between conduction band and valence band is of the order of $$0.07\ eV$$. It is a:

A
insulator

B
conductor

C
semiconductor

D
alloy

Solution
Question 10
1 / -0

If the two ends of a p-n junction are joined by a wire,

A
there will not be a steady current in the circuit

B
there will be a steady current from the n-side to the p-side

C
there will a steady current from the p-side to the n-side

D
there may or may not be a current depending upon the resistance of the connecting wire

Solution