List of top Questions asked in KEAM- 2020

The contribution to the total current in a semiconductor, due to electrons and holes are \(0.75\) and \(0.25\) respectively. The drift velocity of electrons is \(\dfrac{3}{2}\) times that of holes at this temperature. Then the ratio between electron concentration and hole concentration is
A nucleus, initially at rest, breaks up into two nuclear fragments with their radii in the ratio \(2:1\). Then their velocities will be in the ratio
The ratio of the energy released by \(4\) kg of hydrogen at room temperature to the heat generated by \(23.5\) kg of \({}^{235}\text{U}\) in the nuclear reactor by fission process is (Assume energy released per fusion is \(26\) MeV and that per fission is \(200\) MeV)
A certain prism produces a minimum deviation of \(42^\circ\). It produces a deviation of \(45^\circ\) when the angle of incidence is either \(43^\circ\) or \(62^\circ\). The angle of incidence when the prism undergoes minimum deviation is
The reflected ray is completely polarized for certain angle of incidence in a transparent medium. If the angle of refraction is \(30^\circ\), then the refractive index of the medium is
The de Broglie wavelength of the matter wave associated with an object dropped from a height \(x\), when it reaches the ground is proportional to
The number of \(\alpha\)-particles emitted during the radioactive decay chain from \({}^{226}_{88}\text{Ra}\) and ending with \({}^{206}_{82}\text{Pb}\) is
If two waves of intensities \(I\) and \(4I\) superpose, the ratio between maximum and minimum intensities is
Among the following photosensitive substances, the one which emits electrons when it is illuminated by visible light is
If an electromagnetic wave of frequency \(5\) MHz travels from vacuum into a dielectric medium of electric permittivity \(\varepsilon_r=4\), then its
Among the following, which is not true for ultraviolet light?
Choose the wrong statement.
The relation between the charge flow \(\Delta Q\) through the circuit of resistance \(r\) and the change in the magnetic flux \(\Delta \phi_B\) is
Angular width of the first minimum on either side of the central maximum due to a single slit of width \(a\), illuminated by a light of wavelength \(\lambda\) is
The magnetic field at the centre of a circular coil of \(50\) turns and radius \(10\) cm carrying a current of \(1\) A, in tesla is
Choose the wrong statement for the pure inductive circuit.
A train is running at a speed of \(72\ \text{km h}^{-1}\) on the rails separated by a distance of \(150\) cm. If the vertical component of earth's magnetic field at the place is \(4.0\times10^{-5}\) T. The induced emf on the rails is
A transformer operates at \(V_p=6\) kV on the primary side and supplies electric energy at \(V_s=220\) V to a number of houses in a town. If the total power consumption by the town is \(7.2\) kW, the current (in ampere) in the primary is
Choose the wrong statement.
Which one of the following characteristics is not associated with a paramagnetic material?
A coil of \(50\) turns carrying a current of \(2\) A in a magnetic field of \(0.5\) T. The torque acting on the coil is
A long solenoid with \(500\) turns per unit length carries a current of \(1.5\) A. The magnetic induction at one of the ends of the solenoid on its axis in tesla is
Internal resistance of a cell is independent of
Six cells, each of emf \(5\) V and internal resistance \(0.1\ \Omega\) are connected as shown in the figure. The ideal voltmeter \(V\) records the value
The work done in moving a point charge of \(10\mu\text{C}\) through a distance of \(3\) cm along the equatorial axis of an electric dipole is