JEE Main entrance exam Question Bank Solutions for Physics (JEE Main)

A disc of mass M and radius R is placed a rough horizontal surface with its axis horizontal. A light rod of length '2R' is fixed to the disc at point 'A' as shown in figure and a force `3/2` Mg is applied at the other end. If disc starts to roll without slipping the value of "10 × µ_min" where µ_min is minimum coefficient of friction between disc and horizontal surface required for pure rolling is ______.

An artificial satellite is moving in a circular orbit around the earth with a speed equal to half the magnitude of escape velocity from the earth. If the satellite is stopped in its orbit and allowed to fall freely onto the earth, the speed with which it hits the surface ______ km/s.

[g = 9.8 ms^-2 and R_e = 6400 km]

In a cubical box of volume V, there are N molecules of a gas moving randomly. If m is mass of each molecule and v² is the mean square of x component of the velocity of molecules, then the pressure of the gas is ______.

In a fluorescent lamp choke (a small transformer) 100 V of reverse voltage is produced when the choke current changes uniformly from 0.25 A to 0 in a duration of 0.025 ms. The self-inductance of the choke (in mH) is estimated to be ______.

Air separated from the atmosphere by a column of mercury of length h = 15 cm is present in a narrow cylindrical two-soldered at one end. When the tube is placed horizontally the air occupies a volume V₁ = 240 mm³. When it is set vertically with its open end upwards the volume of the air is V₂ = 200 mm³. The atmospheric pressure during the experiment is 7n cm of Hg where n is a single digit number. n will be ______.

An observer looks at a distant tree of height 10 m with a telescope of magnifying power of 20. To the observer the tree appears:

The image formed by an objective of a compound microscope is ______.

Match List -I (Fundamental Experiment) with List -II (its conclusion) and select the correct option from the choices given below the list: 

For a constant collector-emitter voltage of 8V, the collector current of a transistor reached to the value of 6 mA from 4 mA, whereas base current changed from 20 µA to 25 µA value. If transistor is in active state, small signal current gain (current amplification factor) will be ______.

The positive feedback is required by an amplifier to act an oscillator. The feedback here means ______.

An npn transistor operates as a common emitter amplifier, with a power gain of 60 dB. The input circuit resistance is 100Ω and the output load resistance is 10 kΩ. The common emitter current gain β is ______.

In the adjoining figure, AB represents the incident ray, and BK is the reflected ray. If angle BCF = θ, then ∠BFP is given by ______.

A camera objective has an aperture diameter of d. If the aperture is reduced to diameter d/2, the exposure time under identical conditions of light should be made ______.

A heat engine operates between a cold reservoir at temperature T₂ = 400 K and a hot reservoir at temperature T₁. It takes 300 J of heat from the hot re ervoir and delivers 240 J of heat to the cold reservoir in a cycle. The minimum temperature of the hot reservoir has to be ______ K.

Which statement is incorrect?

If `vecA` and `vecB` is two vectors satisfying the relation `vecA.vecB = [vecA xx vecB]`. Then the value of `[vecA - vecB]` will be ______.

A nucleus of mass M emits a γ-ray photon of frequency 'v'. The loss of internal energy by the nucleus is ______.

A block of 200 g mass moves with a uniform speed in a horizontal circular groove, with vertical side walls of radius 20 cm. If the block takes 40 s to complete one round, the normal force by the side walls of the groove is ______.

Which of the following options may be the correct estimate of the mean free path of gas particles? [n: Number of gas particle per unit volume, d: diameter]

A racing car is travelling along a track at a constant speed of 40 m/s. A T.V. cameraman is recording the event from a distance of 30 m directly away from the track as shown in the figure. In order to keep the car under view in the position shown, the angular speed with which the camera should be rotated is ______.