COMEDK 2024 Morning Shift

A coil offers a resistance of \(20 \mathrm{~ohm}\) for a direct current. If we send an alternating current through the same coil, the resistance offered by the coil to the alternating current will be :

A transformer which steps down \(330 \mathrm{~V}\) to \(33 \mathrm{~V}\) is to operate a device having impedance \(110 \Omega\). The current drawn by the primary coil of the transformer is :

The capacitance of a parallel plate capacitor is \(400 \mathrm{~pF}\). It is connected to an ac source of \(100 \mathrm{~V}\) having an angular frequency \(100 \mathrm{~rad~s}^{-1}\). If the rms value of the current is \(4 \mu \mathrm{A}\),...

A coil of inductance \(1 \mathrm{H}\) and resistance \(100 \Omega\) is connected to an alternating current source of frequency \(\frac{50}{\pi} \mathrm{~Hz}\). What will be the phase difference between the current and voltage?

The ratio of the radii of the nucleus of two element \(\mathrm{X}\) and \(\mathrm{Y}\) having the mass numbers 232 and 29 is:

The closest approach of an alpha particle when it make a head on collision with a gold nucleus is \(10 \times 10^{-14} \mathrm{~m}\), then the kinetic energy of the alpha particle is :

Find the binding energy of the tritium nucleus:
[Given: mass of \(1 \mathrm{H}^3=3.01605 \mathrm{~u} ; \mathrm{~m}_{\mathrm{p}}=1.00782 \mathrm{~u} ; \mathrm{~m}_{\mathrm{n}}=1.00866 \mathrm{~u}\).]

A parallel plate capacitor is filled by a dielectric whose relative permittivity varies with the applied voltage (U) as \(\epsilon=2 U\). A similar capacitor with no dielectric is charged to \(U_0=78 \mathrm{~V}\). It is then connected to t...

Which of the following statement is true regarding the centre of mass of a system?

Which of the following graph shows the variation of velocity with mass for the constant momentum?

A metal ball of \(20 \mathrm{~g}\) is projected at an angle \(30^{\circ}\) with the horizontal with an initial velocity \(10 \mathrm{~ms}^{-1}\). If the mass and angle of projection are doubled keeping the initial velocity the same, the rat...

A body is moving along a circular path of radius '\(r\)' with a frequency of revolution numerically equal to the radius of the circular path. What is the acceleration of the body if radius of the path is \(\left(\frac{5}{\pi}\right) m\) ?

A \(500 \mathrm{~W}\) heating unit is designed to operate on a \(400 \mathrm{~V}\) line. If line voltage drops to \(160 \mathrm{~V}\), the percentage drop in heat output will be:

A cell of emf E and internal resistance r is connected to two external resistances \(\mathrm{R_1}\) and \(\mathrm{R_2}\) and a perfect ammeter. The current in the circuit is measured in four different situations:
(a) without any external re...

The resistance of the galvanometer and shunt of an ammeter are \(90 \mathrm{~ohm}\) and \(10 \mathrm{~ohm}\) respectively, then the fraction of the main current passing through the galvanometer and the shut respectively are:

On increasing the temperature of a conductor, its resistance increases because

The current through a conductor is '\(\mathrm{a}\)' when the temperature is \(0^{\circ} \mathrm{C}\). It is '\(\mathrm{b}\)' when the temperature is \(100^{\circ} \mathrm{C}\). The current through the conductor at \(220^{\circ} \mathrm{C}\)...

The threshold frequency for a metal surface is '\(n_0\)'. A photo electric current '\(I\)' is produced when it is exposed to a light of frequency \(\left(\frac{11}{6}\right) \mathrm{n}_{\mathrm{o}}\) and intensity $$\mathrm{I}_{\mathrm{n}}$...

The difference in energy levels of an electron at two excited levels is \(13.75 \mathrm{~eV}\). If it makes a transition from the higher energy level to the lower energy level then what will be the wave length of the emitted radiation?
[giv...

The mass of a particle \(\mathrm{A}\) is double that of the particle \(\mathrm{B}\) and the kinetic energy of \(\mathrm{B}\) is \(\frac{1}{8}\)th that of A then the ratio of the de- Broglie wavelength of A to that of B is:

If the ratio of lengths, radii and Young's Moduli of steel and brass wires in the figure are \(\mathrm{a}, \mathrm{b}\) and \(\mathrm{c}\) respectively, then the corresponding ratio of increase in their lengths would be

Select the unit of the coefficient of mutual induction from the following.

Around the central part of an air cored solenoid of length \(20 \mathrm{~cm}\) and area of cross section \(1.4 \times 10^{-3} \mathrm{~m}^2\) and 3000 turns, another coil of 250 turns is closely wound. A current \(2 \mathrm{~A}\) in the sol...

A metallic rod of \(2 \mathrm{~m}\) length is rotated with a frequency \(100 \mathrm{~Hz}\) about an axis passing through the centre of the circular ring of radius \(2 \mathrm{~m}\). A constant magnetic field \(2 \mathrm{~T}\) is applied pa...

If potential (in volt) in a region is expressed as \(\mathrm{V}(\mathrm{x}, \mathrm{y}, \mathrm{z})=6 \mathrm{xy}-\mathrm{y}+2 \mathrm{yz}\), the electric field (in \(N C^{-1}\)) at point \((1,0,1)\) is

Two metal spheres, one of radius \(\frac{R}{2}\) and the other of radius \(2 \mathrm{R}\) respectively have the same surface charge density They are brought in contact and separated. The ratio of their new surface charge densities is

A square shaped aluminium coin weighs \(0.75 \mathrm{~g}\) and its diagonal measures \(14 \mathrm{~mm}\). It has equal amounts of positive and negative charges. Suppose those equal charges were concentrated in two charges \((+Q\) and $$-Q)$...

Two charges '\(-q\)' each are fixed, separated by distance '\(2 d\)'. A third charge '\(q\)' of mass '\(m\)' placed at the mid-point is displaced slightly by '\(x\)' \((x< < d)\) perpendicular to the line joining the two fixed charges as sh...

Five charges, '\(q\)' each are placed at the comers of a regular pentagon of side '\(a\)' as shown in figure. First, charge from '\(A\)' is removed with other charges intact, then charge at '\(A\)' is replaced with an equal opposite charge....

64 rain drops of the same radius are falling through air with a steady velocity of \(0.5 \mathrm{~cm} \mathrm{~s}^{-1}\). If the drops coalesce, the terminal velocity would be

If \(\mathrm{A}\) is the areal velocity of a planet of mass \(\mathrm{M}\), then its angular momentum is

If the earth has a mass nine times and radius four times that of planet X, the ratio of the maximum speed required by a rocket to pull out of the gravitational force of planet \(\mathrm{X}\) to that of the earth is

A glass of hot water cools from \(90^{\circ} \mathrm{C}\) to \(70^{\circ} \mathrm{C}\) in 3 minutes when the temperature of surroundings is \(20^{\circ} \mathrm{C}\). What is the time taken by the glass of hot water to cool from $$60^{\circ...

A one $\mathrm{kg}$ block of ice at \(-1.5^{\circ} \mathrm{C}\) falls from a height of \(1.5 \mathrm{~km}\) and is found melting. The amount of ice melted due to fall, if \(60 \%\) energy is converted into heat is (Specific heat capacity of...

An electric bulb of volume \(300 \mathrm{~cm}^3\) was sealed off during manufacture at a pressure of \(1 \mathrm{~mm}\) of mercury at \(27{ }^{\circ} \mathrm{C}\). The number of air molecules contained in the bulb is, $$(\mathrm{R}=8.31 \ma...

A cubical box of side \(1 \mathrm{~m}\) contains Boron gas at a pressure of \(100 \mathrm{~Nm}^{-2}\). During an observation time of 1 second, an atom travelling with the rms speed parallel to one of the edges of the cube, was found to make...

A stone of mass \(2 \mathrm{~kg}\) is hung from the ceiling of the room using two strings. If the strings make an angle \(60^{\circ}\) and \(30^{\circ}\) respectively with the horizontal surface of the roof then the tension on the longer st...

Steel is preferred to soft iron for making permanent magnets because,

When two objects are moving along a straight line in the same direction, the distance between them increases by \(6 \mathrm{~m}\) in one second. If the objects move with their constant speed towards each other the distance decreases by $$8 ...

A circular coil of radius \(0.1 \mathrm{~m}\) is placed in the \(\mathrm{X}-\mathrm{Y}\) plane and a current \(2 \mathrm{~A}\) is passed through the coil in the clockwise direction when looking from above. Find the magnetic dipole moment of...

Two circular coils of radius '\(a\)' and '\(2 a\)' are placed coaxially at a distance ' \(x\) and '\(2 x\)' respectively from the origin along the \(\mathrm{X}\)-axis. If their planes are parallel to each other and perpendicular to the $$\m...

Two similar coils $A$ and $B$ of radius '\(r\)' and number of turns '\(N\)' each are placed concentrically with their planes perpendicular to each other. If I and \(2 \mathrm{I}\) are the respective currents passing through the coils then t...

Current flows through uniform, square frames as shown in the figure.
In which case is the magnetic field at the centre of the frame not zero?

For a \(30^{\circ}\) prism when a ray of light is incident at an angle \(60^{\circ}\) on one of its faces, the emergent ray passes normal to the other surface. Then the refractive index of the prism is:

When a particular wave length of light is used the focal length of a convex mirror is found to be \(10 \mathrm{~cm}\). If the wave length of the incident light is doubled keeping the area of the mirror constant, the focal length of the mirr...

A ray of light travelling through a medium of refractive index \(\frac{5}{4}\) is incident on a glass of refractive index \(\frac{3}{2}\). Find the angle of refraction in the glass, if the angle of incidence at the given medium - glass inte...

In the normal adjustment of an astronomical telescope, the objective and eyepiece are \(32 \mathrm{~cm}\) apart. If the magnifying power of the telescope is 7, find the focal lengths of the objective and eyepiece.

A body of mass \(5 \mathrm{~kg}\) at rest is rotated for \(25 \mathrm{~s}\) with a constant moment of force \(10 \mathrm{~Nm}\). Find the work done if the moment of inertia of the body is \(5 \mathrm{~kg} \mathrm{~m}^2\).

In a given semiconductor, the ratio of the number density of electron to number density of hole is \(2: 1\). If \(\frac{1}{7}\)th of the total current is due to the hole and the remaining is due to the electrons, the ratio of the drift velo...

Though \(\mathrm{Sn}\) and \(\mathrm{Si}\) are \(4^{\text {th }}\) group elements, \(\mathrm{Sn}\) is a metal while \(\mathrm{Si}\) is a semiconductor because