List of top Physics Questions

Photons of energy 4.2 eV are incident on a photosensitive material of work function 1.7 eV. If the emitted photoelectrons enter normally into a uniform magnetic field of \(\sqrt{2}\times10^{-4}T\), then the largest radius of the circular path described by the photoelectrons is nearly

If the energy stored in an inductor is 18 mJ when a current of 3 A is passed through it, then the magnetic flux linked with the inductor is

The amplitude of the magnetic field of a plane electromagnetic wave travelling along positive x-axis in vacuum is 6 mT. A particle of charge 5 \(\mu\)C is travelling with a velocity of \(6\times10^{5}ms^{-1}\) along the positive y-axis. If the magnetic field is oriented along positive z-axis, then the maximum force exerted on the particle due to electric field of the wave is

The mean radius of a Rowland ring is 12 cm and it has 3000 turns of wire wound on its ferromagnetic core of relative permeability 500. If the magnetic field inside the core is 5 T, then the magnetizing current is

Two long straight parallel wires P and Q carrying currents of 10 A and 20 A respectively in the same direction are placed in air with a separation of 10 cm between them. Another long straight wire R carrying a current of 5 A in the opposite direction is placed between the wires P and Q and parallel to them at a distance of 5 cm from wire Q. Then the magnitude of the net force acting on wire R per unit length is

In an ac circuit, if the rms value of current is 2 A and the wattless current is \(\sqrt{3}\) A, then the power factor of the circuit is

A parallel plate capacitor consists of two circular plates of radii 5 cm and 10 cm. The centres of the two plates are kept on the same straight line with a separation of 'd' and the plates are completely immersed in a liquid of dielectric constant 18. If the capacitance of the capacitor immersed in the liquid is 250 pF, then the value of 'd' is

At a distance of 20 cm from the centre of a charged conducting sphere of radius 10 cm, the electric field due to the sphere is $9000NC^{-1}$ If an electric charge of 3 µC is placed at a distance of 30 cm from the centre of the sphere, then the electrostatic force acting on the charge is}

A part of an electric circuit is shown in the figure. If the reading of the voltmeter is 100 V and the resistance of the voltmeter is 200 $\Omega$, then the value of the resistance $R_{2}$ is}

The magnetic field required to accelerate deuterons in a cyclotron operated at a frequency of 28 MHz is (Mass of proton $=1.67\times10^{-27}kg$)

If the number density of free electrons in a copper wire is $8.5\times10^{22}cm^{-3}$ and the relaxation time of free electrons in the wire is $2.25\times10^{-14}s$, then the electrical conductivity of copper is (Mass of the electron $=9\times10^{-31}$ kg and charge of the electron $=1.6\times10^{-19}C$)}

Keeping the length of an astronomical telescope constant in normal adjustment, to increase its magnification from 4 to 9, the focal length of the eyepiece is to be decreased by 10 cm. The length of the telescope is

If a 200 cm long steel rod clamped at its middle is vibrated in its fundamental mode with a frequency of 1.25 kHz, then the speed of longitudinal waves in the rod is

When an object is placed at a distance of 40 cm from a convex lens, a real image is formed at a distance V from the lens. If the convex lens is replaced with a concave lens of same focal length, then the change in the position of the image is

The thermodynamic variable on which the average kinetic energy of a gas molecule depends is

In a single slit diffraction experiment, if the third minimum for light of wavelength 4800 Å coincides with the second secondary maximum of another light of wavelength $\lambda$, then the value of is

If a source of sound initially at rest is moving away from a stationery observer with an acceleration of $11~ms^{-2}$, then the time taken for the frequency of sound heard by the observer to become 10% less than the frequency of source is (Speed of sound in air $=330~ms^{-1}$)}

Steam at a temperature of $100^{\circ}C$ is passed into water of mass 90 g such that the temperature of the water increases from $20^{\circ}C$ to $40^{\circ}C$ Then the total mass of the water at $40^{\circ}C$ is}

If the rate of flow of water from a pipe of radius 10 mm is $4.6\pi\times10^{-6}m^{3}s^{-1}$, then the Reynolds number of the flow is (Coefficient of viscosity of water $=10^{-3}Pas$)}

A water drop when pressed between two parallel glass plates spreads in to a circle of diameter 10 cm. If the surface tension of water is $70\times10^{-3}Nm^{-1}$ and the force required to separate the two glass plates is 2.2 N, then the volume of the drop is nearly}

The intensive variables among thermodynamic state variables internal energy U, volume V, pressure P, absolute temperature T and total mass M are

In the strain-stress curve for a material, if the ultimate strength and fracture points are close, then the material is

A comet at infinity starts moving towards the earth and passes the earth at a distance of 4R from the center of the earth, where R is the radius of the earth. If escape velocity of a body from the surface of earth is $11.2~kms^{-1}$, then the maximum velocity of the comet is}

The total energy of a particle executing simple harmonic motion with 2 cm amplitude is 160 mJ. The force acting on the particle at a point where the ratio of the potential and kinetic energies of the particle becomes 1 : 15 is

The radius of gyration of a solid sphere of mass M and radius R about its diameter is K. The radius of gyration of a uniform circular disc of mass 2M and radius $\frac{R}{2}$ about its diameter is}