List of top Questions asked in COMEDK UGET

Pick out the correct statement from the following:

When a metal of work function $4\text{ eV}$ is exposed to radiation, the maximum kinetic energy of the emitted electrons is $4\text{ eV}$. The stopping potential required is:

The atomic mass of an element $_{10}\text{X}^{20}$ is $198170\text{ amu}$. The binding energy per nucleon of that element is: (Given mass of neutron $= 00867\text{ amu}$, mass of proton $= 00783\text{ amu}$, and $1\text{ amu} = 931\text{ MeV}$)}

What is the minimum wavelength of radiation required to detect a p-n junction diode made of a semiconductor having a band gap of $3\text{ eV}$? (Take Planck's constant $h = 6 \times 10^{-34}\text{ J s}$, speed of light $c = 3 \times 10^8\text{ m s}^{-1}$)}

On both sides of a magnetic needle, two short magnets $A$ and $B$ are placed on the same horizontal line which is perpendicular to the magnetic meridian. The south poles of $A$ and $B$ are facing each other, which are $10\text{ cm}$ and $20\text{ cm}$ respectively from the magnetic needle. If the needle remains undeflected, the ratio of the magnetic moment of $A$ to that of $B$ is:

The current through a circular coil is halved and the radius of the coil is doubled. If $B_1$ and $B_2$ are respectively the initial and final magnetic field strengths at the center of the coil, then:

A bullet fired into a door gets embedded exactly at its center, causing the door to rotate about its vertical hinge axis practically without friction with an angular velocity of $625\text{ rad s}^{-1}$. The door is $0\text{ m}$ wide and weighs $12\text{ kg}$. If the mass of the bullet is $10\text{ g}$, find the speed with which it was fired. (Hint: The moment of inertia of the door about the vertical axis at one end is $I = \frac{ML^2}{3}$)}

In a given circuit, the instantaneous values of alternating voltage and current are $V = 5 \sin(80\pi t + \pi)$ volts and $I = 5 \sin(80\pi t)$ amperes respectively. Find the average power consumed in the circuit.

The dimensional formula for specific resistance (resistivity) is:

A galvanometer of resistance $50\text{ }\Omega$ has $30$ divisions and a current sensitivity of $1\text{ mA/div}$. What should be the shunt resistance so that it can be converted into an ammeter of range $10\text{ A}$?

The basic principle behind the working of an electron microscope is:

A uniform electric field of $5 \times 10^3\text{ N C}^{-1}$ is maintained in the positive Y-direction. Now a point charge of $2 \times 10^{-4}\text{ C}$ at rest is released from the origin. The kinetic energy attained by the charge when it is at a distance of $5\text{ m}$ from the origin is:

In a single-slit diffraction experiment, the diffraction pattern is observed on a screen placed at a distance of $2\text{ m}$ from a slit of width $1\text{ mm}$. If the distance between the first dark fringe on either side of the central bright fringe is $2\text{ mm}$, what is the wavelength of the monochromatic light used in this experiment?

A block of mass $5\text{ kg}$ moves along the floor of a hall with an initial speed of $5\text{ m s}^{-1}$. It strikes an uncompressed spring and compresses it till the block becomes motionless. If the force constant of the spring is $10000\text{ N m}^{-1}$ and the spring is compressed by $5\text{ cm}$, calculate the effective force of kinetic friction.

A hydrogen atom absorbs energy and rises to the $n = 3$ state from its ground state $n = 1$. If the potential energy of the atom at its ground state is $-22\text{ eV}$, find the wavelength emitted by it when it returns to its ground state: (Take Planck's constant $= 6 \times 10^{-34}\text{ J s}$, speed of light $= 3 \times 10^8\text{ m s}^{-1}$)}

An electric field of $8 \times 10^{4}\text{ V m}^{-1}$ and a magnetic field of $6 \times 10^{-3}\text{ T}$ are applied simultaneously on an electron beam such that the path of the beam remains undeviated. Then the speed of the electron will be:

A capacitor of capacitance $8\mu\text{F}$ is fully charged by connecting it to a source of $200\text{ V}$. It is then disconnected from the supply and connected to an uncharged capacitor of capacitance $4\mu\text{F}$. The electrostatic energy lost in this sharing process is:

A vessel of volume $27 \times 10^{4}\text{ cc}$ contains a mixture of Hydrogen (molar mass $= 2\text{ g mol}^{-1}$) and Oxygen (molar mass $= 32\text{ g mol}^{-1}$) gas at standard temperature and pressure (S.T.P.). If the mass of hydrogen is $16\text{ g}$, find the mass of oxygen gas contained in the vessel.

The main function of cadmium rods used in a nuclear reactor is to:

A pith ball of mass $m$ grams and charge $Q$ is suspended using a massless silk thread near a large charged conducting metal sheet of area $A$ and surface charge density $\sigma$. If the silk thread makes an angle $\theta$ with the metal sheet, then $\tan\theta$ is equal to:

If the ratio of the nuclear radii of two atoms is $2:3$, then the ratio of their mass numbers is:

Resonance is produced between a tuning fork and a resonance column tube with its upper end open and lower end closed by a water surface. If the frequency of the tuning fork is $800\text{ Hz}$, and the first two resonances are observed at lengths $75\text{ cm}$ and $325\text{ cm}$, find the length at which the third resonance occurs and the speed of sound.

The distance between the objective and eyepiece of an astronomical telescope in normal adjustment is $27\text{ cm}$ and its magnifying power is $8$. What is the focal length of the eyepiece?

A source of alternating emf $e = \varepsilon_0 \sin(\omega t)$ is connected to a pure capacitor. Then the instantaneous current in the circuit is:

The ratio of the angle of deviation produced by a thin prism, when it is placed in air to the angle of deviation produced when it is immersed in water of refractive index $\frac{4}{3}$ is: (Take refractive index of glass $= \frac{3}{2}$)}