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Test: Combined (Thermo + Electronics) - Physics MCQ


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55 Questions MCQ Test GATE Physics Mock Test Series 2025 - Test: Combined (Thermo + Electronics)

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Test: Combined (Thermo + Electronics) - Question 1

For n-p-n transistor connected as shown in figure VBE = 0.7 volts. Given that reverse saturation current of the .junction at room temperature 3000 K is 10-13 A, the emitter current is

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Test: Combined (Thermo + Electronics) - Question 2

In the bistable circuit shown in the figure, the ideal OP- Amp lias saturation levels of ±5 V. The value of R1 (in kΩ) that gives a hysteresis width of 500 mV is______


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Test: Combined (Thermo + Electronics) - Question 3

The circuit shown in the figure is 

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Test: Combined (Thermo + Electronics) - Question 4

Let the magnitude of the gain in the inverting Op-Amp circuit shown be x with switch Sopen. When the switch is closed, the magnitude of gain becomes.

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Test: Combined (Thermo + Electronics) - Question 5

Consider the circuit shown in the figure. Assuming  the value of the dc voltage VC2 (in volt) is _____.


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Test: Combined (Thermo + Electronics) - Question 6

A Weiii bridge oscillator is shown in figure, which of the following statements are true, if f " is the ffeequency of oscillation?

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Test: Combined (Thermo + Electronics) - Question 7

In a voltage follower op-amp circuit, find the closed loop gain V0/Vs if the open loop gain = 2

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Test: Combined (Thermo + Electronics) - Question 8

The circuit shown in figure is best described as a 

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 8

CKT is voltage doubles circuit
⇒ Once capacitor charge it can't discarge

Test: Combined (Thermo + Electronics) - Question 9

In the shunt regulator shown below, the Vz = 8.2 V and VBE = 0.7 V. The regulated output voltage V0 is

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 9

KVL

Test: Combined (Thermo + Electronics) - Question 10

Let  denote the Exclusive OR (XOR) operation, Let '1' and '0' denote the binary constants. Consider the following Boolean expression for F over two variables P and Q:

The equivalent expression for F is

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Test: Combined (Thermo + Electronics) - Question 11

Suppose one Si and one Ge-diodes are connected in parallel and then this combination is connected to a power supply of 5 V together with a series resistance 220 Ω. The value of the current through the Si(I1) and Ge(I2) are
[Given the cut in voltage of Si diode is 0.7 V and Ge diode is 0.3 V]

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 11

Since the cut in voltage of Ge-diode is less than the cut in voltage of Si diode, so first Ge-diode will be on and all current will pass through it and Si diode will never on.

Test: Combined (Thermo + Electronics) - Question 12

In a certain CE amplifier with emitter resistance and emitter by-pass capacitor, if the by-pass capacitor is removed the voltage gain of the amplifier.

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 12

The re model of CE transistor.


Therefore, gain will decrease if we remove capacitor.

Test: Combined (Thermo + Electronics) - Question 13

In the given circuit the time constant is larger than the period of the signal and the zener breakdown voltage of zener diode is 6V. A square wave is applied to the input as shown in figure. Which of the following graph represent the nature of the output.

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 13

During positive half cycle diocle will be conducting so output will be zero and capacitor will changed at -10V. During negative half cycle effective input will -20 V. and diode will be reverse biased and input voltage is less than Vth, so zener diode will be behave like voltage regulator. So output will be -6V.

Test: Combined (Thermo + Electronics) - Question 14

For the Karnaugh map shown in the given figure, the minimum Boolean function is:

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Test: Combined (Thermo + Electronics) - Question 15

The given circuit will behave like

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Test: Combined (Thermo + Electronics) - Question 16

If volume and number of particles (F, N) of a thermodynamic system are doubled, which of the following quantities is bound to be doubled?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 16

Pressure (P), Temperature (T) and Chemical potential (//) are intensive variables whereas entropy (S) is an extensive variable. On increasing the size of a system, extensive variables are bound to increase proportionally whereas intensive variables are not bound to change just because the size of the system has increased.

Test: Combined (Thermo + Electronics) - Question 17

An ideal bose gas in 5-dimensions has the energy dispersion relation ∈ = Aps. For the Bose gas to undergo Bose-Einstein condensation, which of the following should hold?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 17

For Bose-Einstein condensation o f an ideal bose gas is d-dimensions with dispersion relation (S > 0 because increasing momentum should not decrease energy), we have

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Test: Combined (Thermo + Electronics) - Question 18

10 bosons are to be distributed in 3 different energy levels with the 2nd energy level being doubly degenerate and the other two are non-degenerate. The number of ways of achieving this is _____


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 18

3 energy levels with one of them being doubly degenerate effectively means 4 energy levels.
∴ Number of ways of distributing 10 bosons in 4 energy levels

Test: Combined (Thermo + Electronics) - Question 19

For a gas confined in a box of volume V having total energy E and N number of particles, the number of microstates is  Then the equation of state is

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Test: Combined (Thermo + Electronics) - Question 20

A real gas expands into vacuum in thermally insulated container. Winch of the following properties of the gas will not change?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 20

The given case is of adiabatic free expansion. For this, the internal energy of all the gases remains conserved. Moreover, the expression of internal energy of a real gas is given by

∴ 

Since, dV > 0, we have dT < 0. So, the temperature of the real gas will decrease.

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Test: Combined (Thermo + Electronics) - Question 21

Consider a system of 5 non-interacting distinguishable particles. Each particle can occupy only two energy levels ∈ and 2∈. If the total energy of the system 8∈. Then, the entropy of the system is _____ kB. (answer must be given upto 2 decimal places)


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Let N1 and N2 be the number of particles occupying energy levels ∈ and 2∈ respectively.

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Test: Combined (Thermo + Electronics) - Question 22

Bulk modulus of a substance is defined as where kis tlie isothermal compressibility. If instead kT of 1 mole of an ideal gas, we take 5 moles of the same gas, then the ratio of bulk modulus to pressure B:P =_____. (Correct answer must be given upto two place decimal) 


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 22

For ideal gas, we have 

Test: Combined (Thermo + Electronics) - Question 23

Water has the anomalous property that it contracts on melting. It means that 

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 23

By Clausius - Clapeyron equation

where L = Latent heat of fusion, V2 = Volume of water and V1 = Volume of ice 

It means that with increase in pressure, there is decrease in temperature.
Hence, melting point decreases with increase of pressure.

Test: Combined (Thermo + Electronics) - Question 24

Below a certain temperature θ, the molecular specific heat of a certain gas is 5/2 kBAs the temperature is raised above θ , the specific heat becomes 7/2 kB. Which of the following can be the gas in this experiment?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 24

The specific heat of a diatomic molecule looks like

This jump of Cfrom  comes from vibrational degrees of freedom.
Hence, the gas to be nitrogen.

Test: Combined (Thermo + Electronics) - Question 25

For a 2nd order phase transition, which of the following remains continuous?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 25

For a 2nd order phase transition, the quantities which involves second order derivative of free energy are discontinuous whereas the quantities which involves first order derivative of free energy are continuous .Now, we have



As   are 2nd order derivatives of free energy A, they are discontinuous. Moreover, entropy is continuous across 2nd order phase transition.

Test: Combined (Thermo + Electronics) - Question 26

In the Op-Amp circuit shown, assume that the diode current follows the equation   The relationship between 

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Logarithmic Amplifies 
Case-1


Test: Combined (Thermo + Electronics) - Question 27

A regulated power supply, shown in figure below, lias an unregulated input (UR) of 15 volts and generates a regulated ouput. Use the component values shown in the figure.

The power dissipation across the transistor Q1 shown in the figure is

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 27


Test: Combined (Thermo + Electronics) - Question 28

The output voltage of the regulated power supply shown in figure is

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Test: Combined (Thermo + Electronics) - Question 29

Ill the circuit shown, assume that diodes Dand D2 are ideal. In the steady-state condition, the average voltage Vab ( in Volts) across the 0.5 μF capacitor is ______


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Test: Combined (Thermo + Electronics) - Question 30

The figure shows a half-wave rectifier. The diode D is ideal. The average steady state current (in Amperes) through the diode is approximately______


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 30

Positive peak detector circuit


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Test: Combined (Thermo + Electronics) - Question 31

The amplifier circuit shown in the figure is implemented using a compensated operational amplier (OP-Amp). and has an open-loop voltage gain,  and an open - loopcut - off frequency. f= 8Hz.

The voltage gain of the amplifier at 15 kHz. in V/V, is ______


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Test: Combined (Thermo + Electronics) - Question 32

Consider the circuit shown in the figure Assume base-to-emitter voltage VBE = 0.8 V. and common base current gain(α) of the transistor is unity.

The value of the collector-to -emitter voltage VCE (in volts) is ________.


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Test: Combined (Thermo + Electronics) - Question 33

For the given circuit, value of the base current ( Ib ) of the npn transistor will be _____________ mA. ( β is the current gain and assume Op-Amp as ideal).


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Test: Combined (Thermo + Electronics) - Question 34

Transform the following logic circuit (without expressing its switching function) into an equivalent logic circuit that employs only NAND gates each with 2-inputs.

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Test: Combined (Thermo + Electronics) - Question 35

The number of NAND gate required to implement  _______


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Test: Combined (Thermo + Electronics) - Question 36

Non-interacting bosons trapped in a 3-D cubical box of side α (α is very small). For Bose-Einstein condensation, the chemical potential must be equal to

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 36

For Bose-Einstein condensation to occur, the chemical potential must be equal to the ground state energy.

Test: Combined (Thermo + Electronics) - Question 37

Our Sun is projected to be a red-giant star after approximately 5 billion years from now. In the red giant phase, the Light that will be emitted will be mostly infrared around a wavelength of 1μw. The Sun is now at 10000K and emitting mostly around light of 0.5 μm wavelength. From tins information, the surface temperature of the red-giant sun is found to be

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 37

From Wein’s displacement law, we have 

Therefore, the surface temperature of the red-giant sun will be around 5000k.

Test: Combined (Thermo + Electronics) - Question 38

Two identical fermions can occupy any of the four energy levels E, 3E, 5E, 7E. The energy' levels 3E and 5E are doubly degenerate whereas the energy' levels E and IE are non-degenerate. Assuming no spin degeneracy; the partition function is

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 38

The possible configurations are

Test: Combined (Thermo + Electronics) - Question 39

Given a microstate of a system specified by (E, V, N). Which of the following is correct with respect to the given microstate? (The symbols have their usual meaning)

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 39

Given system can be treated as a micro-canonical ensemble in which (E, V, N) are fixed.
There can be many nucrostates complying with the given inicrostate. The switching of the members of the microcanonical ensemble among the nucrostates is governed by quantum evolution of states under the relevant Hamiltonian and has nothing to do with increase or decrease of entropy of the system. Given the state variables (£, V} AO, entropy is already fixed. The system described by a micro- canonical ensemble, has equal probability to be in any inicrostate.
Therefore , the system over along span of tune, spend sequal tune in each microstate .

Test: Combined (Thermo + Electronics) - Question 40

The entropy of a body of fixed volume which radiates a blackbody varies with temperature as:

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The internal energy of the blackbody in thermal equilibrium at temperature T energy radiated by blackbody is given by

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Test: Combined (Thermo + Electronics) - Question 41

A system is in contact with a heat both at temperature T and in contact with a particle reservoir as well. The system contains three accessible energy level 0, E and 2E and it may or may not contain one particle at a tune one of the given energy levels. How many accessible states are possible?


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 41

The possible configurations are

Test: Combined (Thermo + Electronics) - Question 42

The excitations of ferromagnetic are bosonic in nature and are described by a dispersion relation E ∝ k2, where 'E' is the energy and 'k' is the wavevector of die excitation. The average energy of the 3 -dimensional ferromagnet vanes with temperature as (assuming die bosonic excitations to be non-interacting)

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 42

The average energy is given by 

Test: Combined (Thermo + Electronics) - Question 43

Given a system of two spins s1 and s2 each of which can take values +1 and -1. The energy of the system is E = - Js1s2, where J is some positive constant denoting the strength of interaction between the spurs. The minimum energy and the corresponding number of spin configuration are given by

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 43


Test: Combined (Thermo + Electronics) - Question 44

Given a N classical harmonic oscillators in 3-dimension such that the total energy of the system is E ≤ E0. The available phase space volume depends on E0 as

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 44

For N classical harmonic oscillators, we have



Therefore, available phase space volume 

Test: Combined (Thermo + Electronics) - Question 45

A box of volume V contains N molecules of an ideal gas. It is in contact with an empty box of volume 2 V through a permeable wall allowing exchange of molecules. If a measurement is made for the number of particles in the empty' box after a long time of contact. What is the standard deviation seen in the measurement?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 45

Given no other variables involved in the problem the probability of a particle (as a molecule) to be m one of the box depends on the volume of the particular box vis-a-vis the total volume available to the system.
Therefore, probability of occupying the first box. 
and that of occupying the second box, 
Tins is a binary distribution whose standard deviation is given by

Test: Combined (Thermo + Electronics) - Question 46

Two classical particles are distributed on the vertices of a N-sided polygon. Each site can accommodate one particle at a tune. Iftlie adjacent vertices of the polygon are occupied by the particles, the energy of the system increases by E. The mean energy of the system is

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 46

Let we have two classical particles A and B. Let us fix particle A at one vertex and write the partition function for it. The corresponding partition function is

The partition function of the syste m is 


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Test: Combined (Thermo + Electronics) - Question 47

Consider a mole of an ideal diatomic gas undergoing a cyclic process as shown in the figure:

The magnitude of the heat released in the cyclic process is_____ P0V0. (answer must be given upto two place after decimal)


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 47

Along isothermal process AB,

Along Lsobaric process BC,

Along adiabatic process CA, ΔQ = 0
Therefore, heat supplied to the system in the cycle = 

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Test: Combined (Thermo + Electronics) - Question 48

1 kg of water at 270C is mixed with 2 kg of water at 770C. After thermal equilibrium is reached, the change in
entropy of the system is_____J/K. (Answer must be given upto two place after decimal) (Take specific heat of water to be 4.181 kJ/K)


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 48

Using principle of calorimetry, we have
Heat gamed = Heat lost

Test: Combined (Thermo + Electronics) - Question 49

A classical ideal gas. consisting of N particles (.V → ∝ ) is confined in a box of volume F at a certain temperature T and pressure P. In a part of the box, which has volume V0 a measurement is made to count the number of particles present in it. What is the probability that no particle are present inside?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 49

Probability that no particle is inside the volume V0 is
 [∴ All the paiticles then occupy the remaining volume]

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Test: Combined (Thermo + Electronics) - Question 50

In an experiment to understand why a two-level system cannot act as a laser, a student heated the gas inside began looking at a spin system with only two energy states -μH and μH corresponding to parallel alignment and anti-parallel alignment respectively with the magnetic field H. In Ins measurements of ratio of number of spin up to spin down particles as he increased the magnetic field he finds that it never exceeds a number α. What is α? ( answer must be given upto 2 decimal places)


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 50

For a laser action there is a necessary condition of population inversion to be achieved. In a two-level system, Maxwell-Boltzmann statistics does not allow the upper level to have more N/2 atoms in it even at large excitation energies.

Test: Combined (Thermo + Electronics) - Question 51

The entropy of a thermodynamic system is given as   then, temperature of the system α, E0, are positive constants respectively) 

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 51



So, T is always greater than or equal to zero where, T= 0 when E = E0/2

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Test: Combined (Thermo + Electronics) - Question 52

3 non-interacting fermions are confined in a 2-D box of area ‘a2'. If the energy' of the 1st excited state of the system is 


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 52

Energy of a particle in a 2-D box is

where,  is ground state,  is the 1st excited state.
Therefore, 1st excited state has one fermion each in (1,1), (1,2), (2,1) levels.

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Test: Combined (Thermo + Electronics) - Question 53

A particle of mass 2 x l0-15 kg is constrained to move in two-dimensional x-y plane. The particle ls in equilibrium with a thermal bath (kBT = 10-13J). What is the RMS value of the position (in units of metres) of the particle after a time 10 sec if the particle starts from origin at r = 0 seconds?
(answer must be given in integers)


Detailed Solution for Test: Combined (Thermo + Electronics) - Question 53

By Maxwell-Boltman distribution of velocities, we have


Test: Combined (Thermo + Electronics) - Question 54

There is a particle moving in a liquid in 3-D following Brownian motion.What is the root-mean squared displacement o f the particle after 5 minutes if the diffusion constant is 10-2 cm2/s?

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 54

The root-mean squared displacement is given by 

Test: Combined (Thermo + Electronics) - Question 55

A three-level system at thermal equilibrium at temperature T is governed by the Hamiltonian

The average energy of the system is

Detailed Solution for Test: Combined (Thermo + Electronics) - Question 55

The given Hamiltonain is an upper triangular matrix and hence its eigen values are its diagonal elements. So the corresponding eigen values are

∴ The average energy of the system is

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