List of top Questions asked in COMEDK UGET

The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than \(1.24\,\mu m\) is incident on it. The band gap (in eV) for the semiconductor is

In the energy band diagram of a material shown below, open circles and filled circles denote holes and electrons respectively. The material is a

The electric and magnetic fields associated with an electromagnetic wave propagating along \(+z\) axis, can be represented by

A particle moves towards west with a velocity of \(10\,ms^{-1}\). After \(10\,s\) its direction changes towards south and it moves with the same velocity. The average acceleration of the particle is:

In a nuclear fusion reaction, two nuclei \(A\) and \(B\) fuse to produce a nucleus \(C\), releasing an amount of energy \(\Delta E\) in the process. If the mass defects of the three nuclei are \(\Delta M_A\), \(\Delta M_B\) and \(\Delta M_C\) respectively, then which of the following relations is true? ( \(c\) is the speed of light)

Which, of the following is true of the Balmer series of the hydrogen spectrum?
a. The series is in the visible region.
b. The entire series falls in the ultraviolet region
c. The entire series falls in the infrared region
d. The series is partly in the visible region and partly in the infrared region

A planet is 121 times heavier than moon and has a diameter 9 times that of moon. If the escape velocity on the planet is \(v\), then the escape velocity on the moon will be:

From a circular disc of radius \(2R\), a smaller circular disc is cut with radius of the larger disc as its diameter. The centre of the hole is at a distance of \(R\) from the centre of the original disc. The distance of the centre of mass of the remaining portion from the centre is:

An LCR series ac circuit is at resonance with \(10\,V\) each across \(L\), \(C\) and \(R\). If the resistance is halved, the respective voltage across \(R\), \(C\) and \(L\) are

If the binding energy per nucleon in \( ^7_3Li \) and \( ^4_2He \) nuclei are respectively \(5.60\,MeV\) and \(7.06\,MeV\), then energy of \(p\) in the reaction \( p + ^7_3Li \rightarrow 2\,^4_2He \) is

A sonometer string vibrates with a frequency of \(400\,Hz\). When the length of the string is halved and the tension is altered, it begins to vibrate with a frequency of \(200\,Hz\). The ratio of the new tension to the original tension in the string is:

A block of metal A is connected in series with another block of metal B such that the two metal blocks have the same area of cross sections. The thermal conductivity of metal A is \(K\) and the free end of metal A is at \(80^\circ C\). The temperature of the interface is \(60^\circ C\) and the free end of metal B is at \(20^\circ C\). Assuming the two metals have the same thickness, the conductivity of metal B is:

The radius of earth is \(R\) and acceleration due to gravity on its surface is \(g\). The height at which the acceleration due to gravity becomes \(\frac{g}{8}\) is:

The mean energy per molecule for a diatomic gas is:

The resistance of a wire is \(5\,ohm\) at \(25^\circ C\) and \(7\,ohm\) at \(100^\circ C\). The resistance of the wire at \(0^\circ C\) is

In an experiment to measure the density of the material of a sphere, an error of \(2\%\) occurred while measuring the radius of a sphere and an error of \(3\%\) occurred while measuring the mass of the sphere. What is the maximum percentage error in the measurement of density?

Two simple harmonic motions are represented by equations \(y_1 = 0.5 \sin [200\pi t + \frac{\pi}{3}]\) and \(y_2 = 0.5 \cos \pi t\). The phase difference of the velocity of particle 1 with respect to the velocity of particle 2 is:

If voltage across a bulb rated \(220\,V, 50\,W\) drops by \(5\%\) of its rated value, the percentage of the rated value by which the power would decrease is

A bomb of mass \(20\,kg\) at rest explodes into two pieces of masses \(12\,kg\) and \(8\,kg\). If the velocity of \(8\,kg\) mass is \(6\,ms^{-1}\), then the kinetic energy of the other mass is:

A vertical spring of spring constant \(24Nm^{-1}\) is fixed on a table. A ball of mass \(0.5\,kg\) at a height \(2\,m\) above the free upper end of the spring falls vertically on the spring so that the spring is compressed by a distance of \(50\,cm\). The net work done in the process is:

Two identical conducting balls having positive charges \(q_1\) and \(q_2\) are separated by a distance \(r\). If they are made to touch each other and then separated to the same distance, the force between them will be

Two identical conductors of lengths \(l\) and \(3l\) respectively are maintained at the same temperature. They are given potential differences in the ratio \(1:3\). The ratio of their drift velocities is

A Si and a Ge diode has identical physical dimensions. The band gap in Si is larger than that in Ge. On applying identical reverse bias across these diodes,

A charged particle is released from rest in a region of space in which steady and uniform electric and magnetic fields are parallel to each other. The particle will move in a

For the charge configuration shown here, which of the following is not true?