List of top Physics Questions asked in IIT JAM

A particle (𝑝₁) of mass 𝑚 moving with speed 𝑣 collides with a stationary identical particle (𝑝₂). The particles bounce off each other elastically with 𝑝₁ getting deflected by an angle 𝜃 = 30° from its original direction. Then, which of the following statement(s) is/are true after the collision?

A rod of mass 𝑀, length 𝐿 and non-uniform mass per unit length \(λ(x)=\frac{3Mx^2}{L^3},\) is held horizontally by a pivot, as shown in the figure, and is free to move in the plane of the figure. For this rod, which of the following statements are true?

An α particle with energy of 3 MeV is moving towards a nucleus of ⁵⁰Sn. Its minimum distance of approach to the nucleus is 𝑓×10⁻¹⁴ m. The value of 𝑓 is ________ (rounded off to one decimal place).

A spacecraft has speed 𝑣_𝑠=𝑓𝑐 with respect to the earth, where 𝑐 is the speed of light in vacuum. An observer in the spacecraft measures the time of one complete rotation of the earth to be 48 hours. The value of 𝑓 is (rounded off to two decimal places).

Two silicon diodes are connected to a battery and two resistors as shown in the figure. The current through the battery is __________ A (rounded off to two decimal places).

Given: The forward voltage drop across each diode = 0.7 V

The lattice constant (in Å) of copper, which has FCC structure, is _________ (rounded off to two decimal places).
Given: density of copper is 8.91 g cm^-3 and its atomic mass is 63.55 g mol^-1 ; Avogadro’s number = 6.023 × 10²³ mol⁻¹

Consider a spring mass system with mass 0.5 kg and spring constant 𝑘 = 2 Nm^-1 in a viscous medium with drag coefficient 𝑏 = 3 kg s ^-1 . The additional mass required so that the motion becomes critically damped is _______ kg (rounded off to three decimal places)

A single pendulum hanging vertically in an elevator has a time period 𝑇₀ when the elevator is stationary. If the elevator moves upward with an acceleration of 𝑎 = 0.2𝑔, the time period of oscillations is 𝑇₁. Here 𝑔 is the acceleration due to gravity. The ratio\( \frac{𝑇_0}{ 𝑇_1}\) is (rounded off to two decimal places).

The absolute error in the value of sin𝜃 if approximated up to two terms in the Taylor’s series for 𝜃 = 60∘ is ___________ (rounded off to three decimal places).

The sum of the x-components of unit vectors 𝑟̂ ̇ and 𝜃̂̇ for a particle moving with angular speed 2 rad s ^-1 at angle 𝜃 = 215° is__________ (rounded off to two decimal places)

Unit vector normal to the equipotential surface of 𝑉(𝑥, 𝑦, 𝑧) =4𝑥²+𝑦² + 𝑧 at (1,2,1) is given by (𝑎𝑖̂+ 𝑏𝑗̂+ 𝑐𝑘̂). The value of |𝑏| 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).

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

Two digital inputs A and B are given to the following circuit. For A = 1, B = 0, the values of X and Y are :

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

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 ?

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.

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)

The phase velocity v_p of transverse waves on a one-dimensional crystal of atomic separation d is related to the wavevector k as
\(v_p=C\frac{\sin(kd/2)}{(kd/2)}\)
The group velocity of these waves is

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 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).

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

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 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