List of top Physics Questions

A parallel plate capacitor of capacitance \(5\,\mu\text{F}\) is connected to an AC source. If the relation between the potential difference \(V\) (in volt) across the plates of the capacitor and time \(t\) (in second) is \[ V=7\cos(100\pi t), \] then the displacement current between the plates of the capacitor at a time of \(5\,\text{ms}\) is:
When two electric charges are placed at a distance apart in air, the electrostatic force between them is \(400\text{ N}\). If \(\frac13\) of the space between the two charges is filled with a medium of dielectric constant \(4\), then the electrostatic force between them is:
When a current of \(3\text{ A}\) flows through a uniform copper wire of radius \(0.6\text{ mm}\), the average drift speed of the electrons is \(V\). If \(1.5\text{ A}\) current is flowing in another uniform copper wire of radius \(1.2\text{ mm}\), then the average drift speed of the electrons is:
If the angular momentum of an electron revolving in a circular orbit is \(2.1\times10^{-34}\text{ Js}\), then the magnetic moment associated with the electron is (Specific charge of electron \(=1.76\times10^{11}\text{ C kg}^{-1}\)):
The electric potentials at two points A and B are \(+60\text{ V}\) and \(-30\text{ V}\) respectively. If a particle of mass \(20\,\mu\text{g}\) and charge \(+10\,\mu\text{C}\) is released from rest at point A, then the velocity with which the particle reaches point B is:
In Young's double slit experiment, if the light of wavelength \(6000\AA\) is used, the fringe width is \(\beta\). If \(I\) is the intensity of light at a point on the screen where the path difference becomes \(2000\AA\), then the intensity of light at a point on the screen which is located at a distance of \(\frac{\beta}{6}\) from the central maximum is:
One end of a metal wire of length \(100\text{ cm}\) and radius \(0.6\text{ mm}\) is attached to an end of another wire made of the same metal of length \(180\text{ cm}\) and radius \(0.9\text{ mm}\). If the free end of the longer wire is kept at a potential of \(20\text{ V}\) and the free end of the shorter wire is kept at a potential of \(2\text{ V}\), then the potential at the junction of the two wires is:
If a convex lens of focal length \(22.5\text{ cm}\) is moved between an object and a screen placed \(120\text{ cm}\) apart, then the ratio of the minimum and maximum magnifications is:
Two wires A and B made of the same material have equal lengths. If the volumes of wires A and B are in the ratio \(1:8\) and the tensions applied to the wires A and B are in the ratio \(1:2\), then the ratio of the speeds of transverse waves in wires A and B is:
In a Carnot engine, the heat released to the sink is \(22\%\) less than the heat taken from the source. If the temperature of the source is \(127^\circ\text{C}\), then the temperature of the sink is:
In minimum deviation position of a prism made of refractive index \(\sqrt3\), the angle of deviation of the light ray is \(\frac{\pi}{6}\). If a light ray incidents normally on the first face of the prism, then the angle of incidence of the light ray on the second face of the prism is:
The number of gas molecules per unit volume in a vessel is \(2\times10^{25}\text{ m}^{-3}\) and the surface area of each gas molecule is \(12.5\sqrt{2}\times10^{-20}\text{ m}^2\). If all the gas molecules are in motion, then the mean free path of the gas molecules (in \AA) is:
Second harmonic of an open pipe and third harmonic of a closed pipe of length \(75\text{ cm}\) produce \(n\) beats per second. If the fundamental frequency of the open pipe is \(167\text{ Hz}\), then the value of \(n\) is (Speed of sound in air \(=340\text{ ms}^{-1}\)):
Two metal wires A and B of lengths 80 cm and 120 cm respectively having equal cross-sectional area are connected to form a long wire. When the combination is subjected to a tension, the elongations of the wires A and B are 0.8 mm and 1.5 mm respectively. If the Young's modulus of the material of wire A is \(1.6\times10^{11}\text{ Nm}^{-2}\), then the Young's modulus of the material of wire B (in \(10^{11}\text{ Nm}^{-2}\)) is:
Two liquids A and B of masses \(m\) and \(2m\) at temperatures \(30^\circ\text{C}\) and \(50^\circ\text{C}\) respectively are mixed in a vessel of mass \(5m\) which is at a temperature of \(20^\circ\text{C}\). If the ratio of the specific heat capacities of the liquids A and B is \(1:2\) and the specific heat capacity of the material of the vessel is \(0.3\) times the specific heat capacity of liquid A, then the resultant temperature of the mixture is:
A hydraulic lift has pistons of areas \(2\text{ cm}^2\) and \(50\text{ cm}^2\). To lift a car placed on the larger piston by a distance of \(150\text{ cm}\), if the work to be done by the smaller piston is \(18\text{ kJ}\), then the force to be applied on the smaller piston is:
The time period of a body revolving around the earth in a circular orbit of radius \(2R\) is (where \(R\) is radius of the earth; \(g\) - acceleration due to gravity on the surface of the earth):
A metal sphere of density \(9300\text{ kg m}^{-3}\) and radius \(1.5\text{ mm}\) is falling with a terminal velocity \(V\) through a vertical column of liquid of density \(1300\text{ kg m}^{-3}\) and coefficient of viscosity \(\eta\). The terminal velocity of another sphere of the same metal but of radius \(3\text{ mm}\) falling through another liquid of density \(800\text{ kg m}^{-3}\) and coefficient of viscosity \(1.7\eta\) is:
Two rods A and B are made of different materials having thermal conductivities in the ratio \(2:3\). The lengths of the rods A and B are in the ratio \(2:1\) and their volumes are in the ratio \(1:2\). In the steady state, if the temperature differences across the ends of rods A and B are respectively \(60^\circ\text{C}\) and \(\Delta\theta\), the ratio of rates of flow of heat through rods A and B is \(1:16\), then \(\Delta\theta=\)
A boat of mass \(200\,kg\) and length \(10\,m\) is floating on water. If a boy of mass \(50\,kg\) standing at one end of the boat at a distance of \(20\,m\) from the shore moves to the centre of the boat away from the shore, then the distance of the centre of mass of the boat from the shore is:
A cubical block of cork of side \(10\text{ cm}\) is floating in water. When the cork is depressed slightly and then released, if it oscillates with a time period of \(0.5\text{ s}\), then the mass of the block is nearly (Acceleration due to gravity \(=10\text{ ms}^{-2}\)):
A body is projected from a certain height with an initial velocity \(u\) making an angle \(\theta\) above the horizontal. The time taken for its vertical and horizontal displacements to become equal is:
A body of weight \(W\) is hung with the help of a rope of negligible mass from a helicopter moving in a vertical plane. If the vertical upward acceleration and the horizontal acceleration of the helicopter are each equal to the acceleration due to gravity, then the tension in the rope is:
A ladder of length \(3\,m\) and mass \(20\,kg\) leans on a frictionless wall with its feet at rest on the floor \(1\,m\) away from the wall. The reaction force of the wall on the ladder is nearly:
Two forces are acting on a block of mass \(5\,\text{kg}\) as shown in the figure. If the coefficient of kinetic friction between the block and the surface is \(0.25\), then the net work done in accelerating the block for \(15\) seconds is (Acceleration due to gravity \(=10\,\text{ms}^{-2}\)):