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Physics

The rms speeds of the molecules of Hydrogen, Oxygen and Carbondioxide at the same temperature are $ V_H $, $ V_O $ and $ V_C $ respectively then:

2.

In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are $ 50$ divisions on the circular scale, and the main scale moves by $ 0.5 \text{mm} $ on a complete rotation. For a particular observation the reading on the main scale is $ 5 \text{mm} $ and the $ 20^{\text{th}} $ division of the circular scale coincides with reference line. Calculate the true reading.

3.

If $ E $, $ L $, $ M $ and $ G $ denote the quantities as energy, angular momentum, mass and constant of gravitation respectively, then the dimensions of $ P $ in the formula $ P = E L^{2} M^{-5} G^{-2} $ are:

4.

Inside a uniform spherical shell:
(a) The gravitational field is zero.
(b) The gravitational potential is zero.
(c) The gravitational field is same everywhere.
(d) The gravitation potential is same everywhere.
(e) All of the above
Choose the most appropriate answer from the options given below:

5.

The fractional change in the magnetic field intensity at a distance $ r $ from centre on the axis of current carrying coil of radius$ a $ to the magnetic field intensity at the centre of the same coil is: (Take $ r \ll a $).

6.

What equal length of an iron wire and a copper-nickel alloy wire, each of $ 2 \text{mm} $ diameter connected parallel to give an equivalent resistance of $ 3 \Omega $? (Given resistivities of iron and copper-nickel alloy wire are $ 12 \mu\Omega \text{cm} $ and $ 51 \mu\Omega \text{cm} $ respectively).

7.

A solid metal sphere of radius $R$ having charge $q$ is enclosed inside the concentric spherical shell of inner radius $a$ and outer radius $b$ as shown in the figure. The approximate variation electric field $\vec{E}$ as a function of distance $r$ from centre $O$ is given by

8.

A series $ LCR $ circuit driven by $ 300 \, \text{V} $ at a frequency of $ 50 \, \text{Hz} $ contains a resistance $ R = 3 \, \text{k}\Omega $, an inductor of inductive reactance $ X_L = 250\pi \, \Omega $ and an unknown capacitor. The value of capacitance to maximize the average power should be: (Take $ \pi^2 = 10 $ )

9.

Identify the logic operation carried out by the given circuit:

10.

Car $ B $ overtakes another car $ A $ at a relative speed of $ 40 \, \text{ms}^{-1} $. How fast will the image of car $ B $ appear to move in the mirror of focal length $ 10 \, \text{cm} $ fitted in car $ A $, when the car $ B $ is $ 1.9 \, \text{m} $ away from the car $ A $?

11.

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

12.

Two narrow bores of diameter $ 5.0 \, \text{mm} $ and $ 8.0 \, \text{mm} $ are joined together to form a U-shaped tube open at both ends. If this U-tube contains water, what is the difference in the level of two limbs of the tube.
[Take surface tension of water $ T = 7.3 \times 10^{-2} \, \text{N m}^{-1} $, angle of contact $ = 0 $, $ g = 10 \, \text{ms}^{-2} $ and density of water $ = 1.0 \times 10^{3} \, \text{kg m}^{-3} $.]

13.

In a photoelectric experiment ultraviolet light of wavelength $ 280 \, \text{nm} $ is used with lithium cathode having work function $ \phi = 2.5 \, \text{eV} $. If the wavelength of incident light is switched to $ 400 \, \text{nm} $, find out the change in the stopping potential.

$ (h = 6.63 \times 10^{-34} \, \text{J s}, \, c = 3 \times 10^{8} \, \text{m s}^{-1}) $.

14.

In the given figure, the emf of the cell is $ 2.2 \, \text{V} $ and if internal resistance is $ 0.6 \, \Omega $. Calculate the power dissipated in the whole circuit:

15.

The magnitude of vectors $ \overrightarrow{OA} $, $ \overrightarrow{OB} $ and $ \overrightarrow{OC} $ in the given figure are equal. The direction of $ \overrightarrow{OA} + \overrightarrow{OB} - \overrightarrow{OC} $ with x-axis will be:

16.

Statement I: By doping silicon semiconductor with pentavalent material, the electrons density increases.
Statement II: The $ n $-type semiconductor has net negative charge.
In the light of the above statements, choose the most appropriate answer from the options given below:

17.

A particular hydrogen like ion emits radiation of frequency $ 2.92 \times 10^{15} \, \text{Hz} $ when it makes transition from $ n = 3 $ to $ n = 1 $. The frequency in $ \text{Hz} $ of radiation emitted in transition from $ n = 2 $ to $ n = 1 $ will be:

18.

An inductor coil stores $ 64 \, \text{J} $ of magnetic field energy and dissipates energy at the rate of $ 640 \, \text{W} $ when a current of $ 8 \, \text{A} $ is passed through it. If this coil is joined across an ideal battery, find the time constant of the circuit in seconds:

19.

The initial mass of a rocket is $ 1000 \, \text{kg} $. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of $ 20 \, \text{m s}^{-2} $. The gases come out at a relative speed of $ 500 \, \text{m s}^{-1} $ with respect to the rocket:
[Use $ g = 10 \, \text{m /s}^{2} $]

20.

The material filled between the plates of a parallel plate capacitor has resistivity $ 200 \, \Omega \text{m} $. The value of capacitance of the capacitor is $ 2 \, \text{pF} $. If a potential difference of $ 40 \, \text{V} $ is applied across the plates of the capacitor, then the value of leakage current flowing out of the capacitor is: (given the value of relative permittivity of material is $ 50 $).

21.

Two spherical balls having equal masses with radius of $ 5 \, \text{cm} $ each are thrown upwards along the same vertical direction at an interval of $ 3 \, \text{s} $ with the same initial velocity of $ 35 \, \text{m /s}^{} $, then these balls collide at a height of _________ $ \text{m} $. (take $ g = 10 \, \text{m /s}^{2} $)

22.

A source and a detector move away from each other in absence of wind with a speed of $ 20 \, \text{m /s}^{} $ with respect to the ground. If the detector detects a frequency of $ 1800 \, \text{Hz} $ of the sound coming from the source, then the original frequency of source considering speed of sound in air $ 340 \, \text{m /s}^{} $ will be ______ $ \text{Hz} $.

23.

A uniform chain of length $ 3 \, \text{meter} $ and mass $ 3 \, \text{kg} $ overhangs a smooth table with $ 2 \, \text{meter} $ laying on the table. If $ k $ is the kinetic energy of the chain in joule as it completely slips off the table, then the value of $ k $ is ________. (Take $ g = 10 \, \text{m/s}^{2} $)

24.

White light is passed through a double slit and interference is observed on a screen $ 1.5 \, \text{m} $ away. The separation between the slits is $ 0.3 \, \text{mm} $. The first violet and red fringes are formed $ 2.0 \, \text{mm} $ and $ 3.5 \, \text{mm} $ away from the central white fringes. The difference in wavelengths of red and violet light is ______ $ \text{nm} $.

25.

An amplitude modulated wave is represented by $ C_m(t) = 10\big(1 + 0.2 \cos(12560\, t)\big)\sin\big(111 \times 10^4 \, t\big) $ volts. The modulating frequency in $ \text{kHz} $ will be ________.

26.

Two travelling waves produces a standing wave represented by equation.
$ y = 1.0 \, \text{mm} \cos\!\big(1.57 \, \text{cm}^{-1} \big)\,x \sin\!\big(78.5 \, \text{s}^{-1} t\big) $. The node closest to the origin in the region $ x > 0 $ will be at $ x = $ ________ $ \text{cm} $.

27.

Consider a badminton racket with length scales as shown in the figure.

If the mass of the linear and circular portions of the badminton racket are same $ (M) $ and the mass of the threads are negligible, the moment of inertia of the racket about an axis perpendicular to the handle and in the plane of the ring at, $ \dfrac{r}{2} $ distance from the end $ A $ of the handle will be ________ $ M r^2 $.

28.

Two short magnetic dipoles $ m_1 $ and $ m_2 $ each having magnetic moment of $ 1 \, \text{A m}^2 $ are placed at point $ O $ and $ P $ respectively. The distance between $ OP $ is $ 1 \, \text{meter} $. The torque experienced by the magnetic dipole $ m_2 $ due to the presence of $ m_1 $ is ________ $ \times 10^{-7} $ $ \text{N m} $.

29.

A soap bubble of radius $ 3 \, \text{cm} $ is formed inside the another soap bubble of radius $ 6 \, \text{cm} $. The radius of an equivalent soap bubble which has the same excess pressure as inside the smaller bubble with respect to the atmospheric pressure is ________ $ \text{cm} $.

30.

The electric field in a plane electromagnetic wave is given by
$\vec{E} = 200 \cos \left[ \left( \frac{0.5 \times 10^3}{\text{m}} \right) x - \left( 1.5 \times 10^{11} \frac{\text{rad}}{\text{s}} \times t \right) \right] \frac{\text{V}}{\text{m}} \hat{j}$
If this wave falls normally on a perfectly reflecting surface having an area of $100 \text{ cm}^2$. If the radiation pressure exerted by the E.M. wave on the surface during a $10 \text{ minute}$ exposure is $\frac{x}{10^9} \frac{\text{N}}{\text{m}^2}$. Find the value of $x$.

JEE Main 2021 26th August Morning Shift

Physics Chemistry Mathematics

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The initial mass of a rocket is $ 1000 \, \text{kg} $. Calculate at what rate the fuel should be burnt so that the rocket is given an acceleration of $ 20 \, \text{m s}^{-2} $. The gases come out at a relative speed of $ 500 \, \text{m s}^{-1} $ with respect to the rocket:
[Use $ g = 10 \, \text{m /s}^{2} $]

JEE MainsJEE AdvanceBITSATJEE Mains | PYQ

JEE Mains JEE Advance BITSAT
JEE Mains | PYQ