List of top Questions asked in IIT JAM

In a dielectric medium of relative permittivity 5, the amplitudes of the displacement current and conduction current are equal for an applied sinusoidal voltage of frequency f = 1 MHz. The value of conductivity (in Ω^-1m^-1) of the medium at this frequency is

In the circuit shown, assuming the current gain β = 100 and V_BE = 0.7 V, what will be the collector voltage V_C in V ?
Given : V_CC = 15 V, R₁ = 100 kΩ, R₂ = 50 kΩ, R_C = 4.7 kΩ, and R_E = 3.3 kΩ

A uniform stick of length l and mass m pivoted at its top end is oscillating with an angular frequency ω_r . Assuming small oscillations, the ratio ω_r/ω_s , where ω_s is the angular frequency of a simple pendulum of the same length, will be

At the planar interface of two dielectrics, which of the following statements related to the electric field (\(\vec{𝐸}\) ), electric displacement (\(\vec{D}\)) and polarization (\(\vec{P}\) ) is true ?

Consider a system of large number of particles that can be in three energy states with energies 0 meV, 1 meV, and 2 meV. At temperature T = 300 K, the mean energy of the system (in meV) is closest to
Given: Boltzmann constant k_B = 0.086 meVK^-1

For the Maxwell-Boltzmann speed distribution, the ratio of the root-mean-square speed (v_rms) and the most probable speed (v_max) is
Given : Maxwell-Boltzmann speed distribution function for a collection of particles of mass m is
\(f(v)=(\frac{m}{2\pi k_BT})^{3/2}4\pi v^2\text{exp}(-\frac{mv^2}{2k_BT})\)
where, v is the speed and k_BT is the thermal energy.

In an extrinsic p-type semiconductor, which of the following schematic diagram depicts the variation of the Fermi energy level (E_F) with temperature (T) ?

A container is occupied by a fixed number of non-interacting particles. If they are obeying Fermi-Dirac, Bose-Einstein, and Maxwell-Boltzmann statistics, the pressure in the container is P_FD, P_BE and P_MB, respectively. Then

In a X-Ray tube operating at 20 kV, the ratio of the de-Broglie wavelength of the incident electrons to the shortest wavelength of the generated X-rays is ________ (rounded off to two decimal places).
Given: e/m ratio for an electron = 1.76×10¹¹ Ckg-1 and the speed of light in vacuum is 3×10⁸ ms ^-1

A point source emitting photons of 2 eV energy and 1 W of power is kept at a distance of 1m from a small piece of a photoelectric material of area 10^-4 m² . If the efficiency of generation of photoelectrons is 10%, then the number of photoelectrons generated are 𝑓×10¹² per second. The value of 𝑓 is __________ (rounded off to two decimal places).
Given: 1eV = 1.6 × 10⁻¹⁹ J

Consider the 𝛼-decay ⁹⁰𝑇ℎ ²³²→⁸⁸𝑅𝑎 ²²⁸ . In an experiment with one gram of ⁹⁰𝑇ℎ ²³², the average count rate (integrated over the entire volume) measured by the 𝛼-detector is 3000 counts s ^-1 . If the half life of ⁹⁰𝑇ℎ ²³² is given as 4.4 × 10¹⁷ s, then the efficiency of the 𝛼-detector is ______(rounded off to two decimal places).
Given: Avogadro’s number = 6.023 × 1023 mol⁻¹

In the Thomson model of hydrogen atom, the nuclear charge is distributed uniformly over a sphere of radius 𝑅. The average potential energy of an electron confined within this atom can be taken as \(V=\frac{e^2}{4{\pi}e_0R}\) . Taking the uncertainty in position to be the radius of the atom, the minimum value of 𝑅 for which an electron will be confined within the atom is estimated to be 𝑓 × 10⁻¹¹ m. The value of 𝑓 is _______ (rounded off to one decimal place). 
Given: The uncertainty product of momentum and position is ℏ = 1×10⁻³⁴ Js ^-1 ,e=1.6 × 10⁻¹⁹C, and \(\frac{1}{4{\pi}e_0}\)= 9 × 10⁹ Nm2C ⁻²

The sum of the eigenvalues 𝜆₁ and 𝜆₂ of matrix 𝐵 = 𝐼+𝐴+𝐴² , where
\( \left[ {\begin{array}{cc}  2&1 \\     -0.5 &0.5 \\   \end{array} } \right]\)
 is_____ (rounded off to two decimal places).

A container of volume 𝑉 has helium gas in it with 𝑁 number of He atoms. The mean free path of these atoms is 𝜆_He. Another container has argon gas with the same number of Ar atoms in volume 2𝑉 with their mean free path being 𝜆_Ar. Taking the radius of Ar atoms to be 1.5 times the radius of He atoms, the ratio 𝜆_Ar⁄𝜆_He is__________ (rounded off to two decimal places).

Three frames 𝐹₀, 𝐹₁ and 𝐹₂ are in relative motion. The frame 𝐹₀ is at rest, 𝐹₁ is moving with velocity 𝑣1𝑖̂with respect to 𝐹₀ and 𝐹₂ is moving with velocity 𝑣₂𝑖̂ with respect to 𝐹₁. A particle is moving with velocity 𝑣3𝑖̂ with respect to 𝐹₂. If 𝑣₁ = 𝑣₂ = 𝑣₃= \(\frac{𝑐}{2}\), where 𝑐 is the speed of light, the speed of the particle with respect to 𝐹₀ is 𝑓𝑐. The value of 𝑓 is ____________ (rounded off to two decimal places)

A fission device explodes into two pieces of rest masses 𝑚 and 0.5𝑚 with no loss of energy into any other form. These masses move apart respectively with speeds \(\frac{c}{ √13} \) and \(\frac{c}{2}\) , with respect to the stationary frame. If the rest mass of the device is 𝑓𝑚 then 𝑓 is________ (rounded off to two decimal places).

A conducting wire AB of length m has resistance of .6 Ω. It is connected to a voltage source of 0.5 V with negligible resistance as shown in the figure. The corresponding electric and magnetic fields give Poynting vectors 𝑆 (𝑟 ) all around the wire. Surface integral ∫ 𝑆 . 𝑑𝑎 is calculated over a virtual sphere of diameter 0.2 m with its centre on the wire, as shown. The value of the integral is ______W (rounded off to three decimal places)

For a cubic unit cell, the dashed arrow in which of the following figures represents the direction [220] ?

Which of the following statements about the viscosity of a dilute ideal gas is correct ?

The plot of the function f(x) = ||x| - 1| is

Temperature (T) dependence of the total specific heat (C_v) for a two dimensional metallic solid at low temperatures is

For the following circuit, choose the correct waveform corresponding to the output signal (V_out). Given V_in = 5 sin(200πt) V, forward bias voltage of the diodes (D and Z) = 0.7 V and reverse Zener voltage = 3 V.

In the given circuit, with an ideal op-amp for what value of \(\frac{R_1}{R_2}\) the output of the amplifier V_out = V₂ - V₁ ?

The spectral energy density u_T(λ) vs wavelength (λ) curve of a black body shows a peak at λ = λ_max. If the temperature of the black body is doubled, then

A periodic function f(x) = x² for -π < x < π is expanded in a Fourier series. Which of the following statement(s) is/are correct ?