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

In a Screw Gauge, the 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 mm on a complete rotation. For a particular observation, the reading on the main scale is 5 mm and the 20^th division of the circular scale coincides with the reference line. Calculate the true reading.

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 = EL²M⁻⁵G⁻² are ______.

In a reactor, 2 kg of ₉₂U²³⁵ fuel is fully used up in 30 days. The energy released per fission is 200 Me V given that the Avogadro number, N = 6.023 × 10²⁶ per kilo mole and 1 eV = 1.6 × 10^-19 J. The power output of the reactor is close to :

A long string, having a cross-sectional area 0.80 mm² and density 12.5 g/cm³ is subjected to a tension of 64 N along the x-axis. One end of the string is attached to a vibrator moving in transverse direction. At t = 0, the source is at maximum displacement y = 1 cm. Find the speed of wave travelling on the string.

The dependence of g on geographical latitude at sea level is given by `g = g_0(1 + betasin^2Phi)` where Φ is the latitude angle and β is a dimensionless constant. If Δg is the error in the measurement of g then the error in measurement of latitude angle is ______.

The greatest speed of transverse waves through a steel wire of radius 1 mm is ______ × 10² m. The breaking stress of steel is 6.0 × 10⁸ Nm^-2. Density of steel = 7800 kg m^-3.

Two light beams of intensities in the ratio of 9 : 4 are allowed to interfere. The ratio of the intensity of maxima and minima ______.

A travelling microscope has 20 divisions per cm on the main scale while its Vernier scale has total 50 divisions and 25 Vernier scale divisions are equal to 24 main scale divisions, what is the least count of the travelling microscope?

A travelling microscope is used to determine the refractive index of a glass slab. If 40 divisions are there in 1 cm on main scale and 50 Vernier scale divisions are equal to 49 main scale divisions, then least count of the travelling microscope is ______ × 10^-6 m. 

The least count of the main scale of a screw gauge is 1 mm. The minimun number of divisions on its circular scale required to measure 5 µm diameter of a wire is ______.

If the zero of the vernier lies on the right-hand side and the fourth division coincides with the main scale division when the jaws are in contact so the correction will be ______.

The radius in kilometers to which the present radius of the earth (R = 6400 km) is to be compressed so that the escape velocity is increased 10 times is ______.

A Carnot engine has efficiency of 50%. If the temperature of sink is reduced by 40°C, its efficiency increases by 30%. The temperature of the source will be ______.

The efficiency of a Carnot's engine, working between steam point and ice point, will be ______.

Consider two satellites S₁ and S₂ with periods of revolution 1 hr, and 8 hr, respectively revolving around a planet in circular orbits. The ratio of angular velocity of satellite S₁ to the angular velocity of satellite S₂ is ______.

A circular disc reaches from top to bottom of an inclined plane of length 'L'. When it slips down the plane, it takes time ' t₁'. when it rolls down the plane, it takes time t₂. The value of `t_2/t_1` is `sqrt(3/x)`. The value of x will be ______.

There is a uniform spherically symmetric surface charge density at a distance R_o from the origin. The charge distribution is initially at rest and starts expanding because of mutual repulsion. The figure that represents best the speed V (R(t)) of the distribution as a function of its instantaneous radius R(t) is:

A square loop is carrying a steady current I and the magnitude of its magnetic dipole moment is m. If this square loop is changed to a circular loop and it carries the same current, the magnitude of the magnetic dipole moment of circular loop will be:

Two strings A and B, made of same material, are stretched by same tension. The radius of string A is double of the radius of B. A transverse wave travels on A with speed `v_A` and on B with speed `v_B`. The ratio `v_A/v_B` is ______.

Two balls A and B are placed at the top of 180 m tall tower. Ball A is released from the top at t = 0 s. Ball B is thrown vertically down with an initial velocity 'u' at t = 2 s. After a certain time, both balls meet 100 m above the ground. Find the value of 'u' in ms^-1. [use g = 10 ms ^-2]: