Semiconductors & Communication · JEE Main previous year questions

1. A.$\frac{1+\sin \alpha }{1-\sin \alpha }$
2. B.$\frac{1+\cos \alpha }{1-\cos \alpha }$
3. C.$\frac{1+\tan \alpha }{1-\tan \alpha }$
4. D.$\frac{1+\sin \alpha }{1-\cos \alpha }$

The current voltage relation of diode is given by $I=\left(e^{1000V/T}-1\right)\mathrm{mA}$, where the applied voltage $V$ is in volts and the temperature $T$ is in degree kelvin. If a student makes an error measuring $\pm 0.01\mathrm{V}$ while measuring the current of $5\mathrm{mA}$ at $300\mathrm{K}$, what will be the error in the value of current in $\mathrm{mA}$?

1. A.$0.2\mathrm{mA}$
2. B.$0.02\mathrm{mA}$
3. C.$0.5\mathrm{mA}$
4. D.$0.05\mathrm{mA}$

1. A.
2. B.
3. C.
4. D.

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: If you push on a cart being pulled by a horse so that it does not move, the cart pushes you back with an equal and opposite force. Statement 2: The cart does not move because the force described in statement 1 cancel each other.

1. A.Statement 1 is true, Statement 2 is true, Statement 2 is the correct explanation of Statement 1.
2. B.Statement 1 is false, Statement 2 is true.
3. C.Statement 1 is true, Statement 2 is false.
4. D.Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation of Statement 1.

1. A.NAND gate
2. B.NOR gate
3. C.AND gate
4. D.OR gate

1. A.
2. B.
3. C.
4. D.

1. A.NAND gate
2. B.OR gate
3. C.NOR gate
4. D.AND gate

Broadcasting antennas are generally

1. A.vertical type
2. B.both vertical and horizontal type
3. C.omni directional type
4. D.horizontal type

If the ratio of the concentration of electrons to that of holes in a semiconductor is $\frac{7}{5}$ and the ratio of currents is $\frac{7}{4}$, then what is the ratio of their drift velocities?

1. A.$\frac{5}{8}$
2. B.$\frac{4}{5}$
3. C.$\frac{5}{4}$
4. D.$\frac{4}{7}$

1. A.$1.71\mathrm{A}$
2. B.$2.00\mathrm{A}$
3. C.$2.31\mathrm{A}$
4. D.$1.33\mathrm{A}$

1. A.
2. B.
3. C.
4. D.

1. A.All $E_c,E_g,E_v$ increase
2. B.$E_c$ and $E_v$ increase, but $E_g$ decreases
3. C.$E_c$ and $E_v$ decrease, but $E_g$ increases
4. D.All $E_c,E_g,E_v$ decrease

In a common base mode of a transistor, the collector current is $5.488\mathrm{mA}$ for an emitter current of $5.60\mathrm{mA}$. The value of the base current amplification factor ($\beta$) will be

1. A.49
2. B.50
3. C.51
4. D.48

A particle is moving eastwards with a velocity of $5m/s$. In $10$ seconds the velocity changes to $5m/s$ northwards. The average acceleration in this time is

1. A.$\frac{1}{2}\mathrm{m}{\mathrm{s}}^{-2}$ towards north
2. B.$\frac{1}{\sqrt{2}}\mathrm{m}{\mathrm{s}}^{-2}$ towards north-east
3. C.$\frac{1}{\sqrt{2}}\mathrm{m}{\mathrm{s}}^{-2}$ towards north-west
4. D.zero

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than $2480\mathrm{nm}$ is incident on it. The band gap in $(eV)$ for the semiconductor is

1. A.$2.5\mathrm{eV}$
2. B.$1.1\mathrm{eV}$
3. C.$0.7\mathrm{eV}$
4. D.$0.5\mathrm{eV}$

In a common base amplifier, the phase difference between the input signal voltage and output voltage is

1. A.$\pi$
2. B.$\frac{\pi }{4}$
3. C.$\frac{\pi }{2}$
4. D.$0$

When $p$-$n$ junction diode is forward biased then

1. A.both the depletion region and barrier height are reduced
2. B.the depletion region is widened and barrier height is reduced
3. C.the depletion region is reduced and barrier height is increased
4. D.both the depletion region and barrier height are increased

When $npn$ transistor is used as an amplifer

1. A.electrons move from collector to base
2. B.holes move from emitter to base
3. C.electrons move from base to collector
4. D.holes move from base to emitter

For a transistor amplifier in common emitter configuration for load impedance of $1k\Omega$ $(h_{fe}=50$ and $h_{oe}=25\mu A/V)$ the current gain is

1. A.$-24.8$
2. B.$-15.7$
3. C.$-5.2$
4. D.$-48.78$

If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should

1. A.increase
2. B.remain unchanged
3. C.decrease
4. D.first increase then decrease

The energy band gap is maximum in

1. A.metals
2. B.superconductors
3. C.insulator
4. D.semiconductor

The part of a transistor which is most heavily doped to produce large number of majority carriers is

1. A.emmiter
2. B.base
3. C.collector
4. D.can be any of the above three