List of top Physics Questions

A circular disc \( X \) of radius \( R \) made from iron plate of thickness \( t \) has moment of inertia \( I_x \) about an axis passing through the centre of the disc and perpendicular to its plane. Another disc \( Y \) of radius \( 3R \) made from an iron plate of thickness \( \frac{t}{3} \) has moment of inertia \( I_y \) about the axis same as that of disc X. The relation between \( I_x \) and \( I_y \) is:

To what depth must a rubber ball be taken in deep sea so that its volume is decreased by 0.2%? The bulk modulus of rubber is \( 9.8 \times 10^8 \, \text{N/m}^2 \) and the density of sea water is \( 10^3 \, \text{kg/m}^3 \) (g = 9.8 m/s\(^2\))

Light of frequency 2 times the threshold frequency is incident on a photo-sensitive material. If the frequency is made \( \frac{1}{3} \)rd and intensity is doubled then the photocurrent will:

The surface density of charge on the surface of a charged conductor in air is \( 0.885 \, \mu C/m^2 \). The outward force per unit area of charged conductor is:

An electron moving with initial velocity \( \mathbf{V} = V_0 \hat{i} \) is moving in a magnetic field \( \mathbf{B} = B \hat{k} \). Then its de-Broglie wavelength:

Two identical wires of same length are vibrating in unison with a tuning fork, under same tension. The length of one wire is decreased by 1 cm and it produces 3 beats per second with the tuning fork. The length of the other wire is increased by 1 cm and it produces 2 beats per second with the tuning fork. If the original length of wire is 67 cm, the frequency of the tuning fork is:

The r.m.s. velocity of hydrogen molecules at temperature \( T \) is seven times the r.m.s. velocity of nitrogen molecules at 300 K. This temperature \( T \) is (Molecular weights of hydrogen and nitrogen are 2 and 28 respectively):

In the following circuit, the internal resistance of the cell is 5 \( \Omega \), the current drawn from the cell will be:

A particle of mass \( m \) is rotating in a horizontal circle of radius \( r \) with uniform velocity \( \mathbf{V} \). The change in its momentum at two diametrically opposite points will be:

The angle of polarisation for a medium is 60°. The critical angle for this will be \( \left( \tan 60^\circ = \sqrt{3} \right) \):

In hydrogen atom, during the transition of electron from \( n \)th outer orbit to first Bohr orbit, a photon of wavelength \( \lambda \) is emitted. The value of \( n \) is: [\( R \) = Rydberg's constant]

Two rings of radii \( R \) and \( nR \) made from the same wire have the ratio of moments of inertia about an axis passing through their centre and perpendicular to the plane of the rings is 1 : 8. The value of \( n \) is:

In a series LCR circuit at resonance, the applied e.m.f. of the source and current in the circuit are:

If the frequency of oscillation of a simple pendulum in simple harmonic motion is \( n \), then frequency of oscillation of simple pendulum when length is 4 times is:

The length of antenna required to transmit the signals of frequency \( 1.5 \times 10^8 \) Hz is [velocity of light in air, \( c = 3 \times 10^8 \, \text{m/s} \)]

If \( I \) is the moment of inertia and \( L \) is angular momentum of a rotating body, then \( \frac{L^2}{2I} \) is its:

The sensitivity of a milliammeter of range 0 to 50 mA is \( \frac{x}{\text{div}} \, \text{mA} \). If it is converted into an ammeter of range 500 mA by using a suitable shunt then the sensitivity will be:

A particle of mass 4 gram moves along a circle of radius \( 10^2 / 2\pi \) cm with constant tangential acceleration. After beginning of the motion, by the end of second revolution, the kinetic energy of the particle becomes \( 18 \times 10^{-5} \) J. The magnitude of tangential acceleration is:

Let the physical quantity be \( x = \frac{a^3b^2}{c} \). If the percentage error in the measurement of \( a \), \( b \), and \( c \) is 2%, 3%, and 4% respectively, then the percentage error in the measurement of \( x \) is:

The phase difference between the voltage and the current in an a.c. circuit is \( \frac{\pi}{4} \). If the frequency is 50 Hz, then the phase difference is equivalent to a time of:

The bob of a simple pendulum is released at time \( t = 0 \) from a position of small angular displacement. Its linear displacement is \( l \) (length of simple pendulum) and \( g \) (acceleration due to gravity), \( A \) = amplitude of S.H.M.

Following graph shows the variation of load (\( W \)) versus elongation (\( l \)) for four wires of the same length and material represented by lines OP, OQ, OR, and OS. Which line represents the thickest wire?

In the following circuit, what is the voltage across PQ?

A block of mass \( m \) moving on a frictionless surface at speed \( V \) collides elastically with a block of same mass, initially at rest. Now the first block moves at an angle \( \theta \) with its initial direction and has speed \( V_1 \). The speed of the second block after collision is:

A charge \( q \) is circulating with constant speed \( V \) in a semi-circular loop of wire of radius \( R \). The magnetic moment of this loop is: