List of practice Questions

A ray of laser of a wavelength 630 nm is incident at an angle of $30^\circ$ at the diamond-air interface. It is going from diamond to air. The refractive index of diamond is 2.42 and that of air is 1. Choose the correct option.

An inductor of 10 mH is connected to a 20 V battery through a resistor of 10 k$\Omega$ and a switch. After a long time, when maximum current is set up in the circuit, the current is switched off. The current in the circuit after 1 $\mu$s is $\frac{x}{100}$ mA. Then $x$ is equal to ________. (Take $e^{-1} = 0.37$)

A circular conducting coil of radius 1 m is being heated by the change of magnetic field $\vec{B}$ passing perpendicular to the plane in which the coil is laid. The resistance of the coil is 2 $\mu\Omega$. The magnetic field is slowly switched off such that its magnitude changes in time as \[ B = \frac{4}{\pi} \times 10^{-3} \text{T} \left( 1 - \frac{t}{100} \right) \] The energy dissipated by the coil before the magnetic field is switched off completely is E = ________ mJ.

Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her as non-uniform and distorted. The doctor diagnosed the problem as :

A refrigerator consumes an average 35 W power to operate between temperature -10$^{\circ}$C to 25$^{\circ}$C. If there is no loss of energy then how much average heat per second does it transfer ?

An electric appliance supplies 6000 J/min heat to the system. If the system delivers a power of 90 W. How long it would take to increase the internal energy by $2.5 \times 10^3$ J ?

An ideal gas is expanding such that $PT^3 = \text{constant}$. The coefficient of volume expansion of the gas is :

The height of victoria falls is 63 m. What is the difference in temperature of water at the top and at the bottom of fall?
[Given 1 cal = 4.2 J and specific heat of water = 1 cal g$^{-1}$ $^{\circ}$C$^{-1}$]

A heat engine operates between a cold reservoir at temperature T$_2$ = 400 K and a hot reservoir at temperature T$_1$. It takes 300 J of heat from the hot reservoir and delivers 240 J of heat to the cold reservoir in a cycle. The minimum temperature of the hot reservoir has to be _________ K.

For an ideal gas the instantaneous change in pressure 'p' with volume 'v' is given by the equation $\frac{dp}{dv} = -ap$. If $p = p_0$ at $v = 0$ is the given boundary condition, then the maximum temperature one mole of gas can attain is : (Here R is the gas constant)

A reversible engine has an efficiency of $\frac{1}{4}$. If the temperature of the sink is reduced by $58^\circ\text{C}$, its efficiency becomes double. Calculate the temperature of the sink :

A sample of gas with $\gamma = 1.5$ is taken through an adiabatic process in which the volume is compressed from 1200 $cm^3$ to 300 $cm^3$. If the initial pressure is 200 kPa. The absolute value of the workdone by the gas in the process = ________ J.

Thermodynamic process is shown below on a P-V diagram for one mole of an ideal gas. If $V_2=2V_1$ then the ratio of temperature $T_2/T_1$ is: The process is $PV^{1/2}$ = constant.

A reversible heat engine converts one-fourth of the heat input into work. When the temperature of the sink is reduced by 52 K, its efficiency is doubled. The temperature in Kelvin of the source will be ________ .

In the reported figure, there is a cyclic process ABCDA on a sample of 1 mol of a diatomic gas. The temperature of the gas during the process A $\rightarrow$ B and C $\rightarrow$ D are $T_1$ and $T_2$ ($T_1>T_2$) respectively. Choose the correct option out of the following for work done if processes BC and DA are adiabatic.

A diatomic gas, having $C_p = \frac{7}{2}R$ and $C_v = \frac{5}{2}R$, is heated at constant pressure. The ratio $dU : dQ : dW$:

In a thermodynamical process, $P = kV^3$. The work done when the temperature changes from 100°C to 300°C will be ________ nR.

A perfect gas undergoes a cyclic process ABCA. A→B: Isothermal expansion ($V_1 \to 2V_1$). B→C: Isobaric compression to $V_1$. C→A: Isochoric change to $P_1$. Total work done is :

Match List I with List II.
List I: (a) Isothermal (b) Isochoric (c) Adiabatic (d) Isobaric.
List II: (i) Pressure constant (ii) Temperature constant (iii) Volume constant (iv) Heat content constant.

For an adiabatic expansion of an ideal gas, the fractional change in its pressure is equal to (where $\gamma$ is the ratio of specific heats):

An ideal gas in a cylinder is separated by a piston in such a way that the entropy of one part is $S_1$ and that of the other part is $S_2$. Given that $S_1>S_2$. If the piston is removed then the total entropy of the system will be:

One mole of an ideal gas is taken through an adiabatic process where the temperature rises from $27^\circ\text{C}$ to $37^\circ\text{C}$. If the ideal gas is composed of polyatomic molecule that has 4 vibrational modes, which of the following is true?
[R = 8.314 J mol$^{-1}$ K$^{-1}$]

Two Carnot engines A and B operate in series such that engine A absorbs heat at $T_1$ and rejects heat to a sink at temperature T. Engine B absorbs half of the heat rejected by Engine A and rejects heat to the sink at $T_3$. When workdone in both the cases is equal, the value of T is :

For a gas $C_p - C_v = R$ in a state P and $C_p - C_v = 1.10 R$ in a state Q. $T_P$ and $T_Q$ are the temperatures in two different states P and Q respectively. Then

A monoatomic ideal gas, initially at temperature $T_1$, is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature $T_2$ by releasing the piston suddenly. If $l_1$ and $l_2$ are the lengths of the gas column, before and after the expansion respectively, then the value of $\frac{T_1}{T_2}$ will be :