COMEDK 2021

The formula of capacitative reactance is

For the same resonant frequency, if L is changed from L to \({L \over 3}\), then capacitance should change from C to

What should be the value of self-inductance of an inductor that should be connected to 220 V 50 Hz supply, so that a maximum current of 0.9 A flows through it?

If impedance is \(\sqrt3\) times of resistance, then find phase difference.

The Lyman series of a hydrogen atom belongs
in which category

If an electron in hydrogen atom jumps from an orbit of level \(n=3\) to an orbit at level \(n=2\), emitted radiation has a frequency of
(R = Rydberg's constant and c = velocity of light)

Ba-122 has half-life of 2 min. Experiment has to be done using Ba-122 and it takes 10 min to set up the experiment. It initially 80 g at Ba-122 was taken, how much Ba was left when experiment was started?

When the speed of light becomes \(\frac{2}{3}\) of its present value, then the energy released in a given atomic explosion would

Which of the following quantity represents the dimensions of momentum?

Centre of mass of the given system of particles will be at

When two bodies collide with each other such that their kinetic energy remains constant. Their collision is said to be

When a car of mass \(m\) is moving with speed \(v\) along a circle of radius \(r\) on a level road, the centripetal force is provided by \(f\), where \(f\) denotes
(\(\mu_s\) \(\to\) coefficient of friction, N \(\to\) normal reaction)

In detector, output circuit consists of \(R=10~k\Omega\) and \(C=100~pF\). The frequency of carrier signal which it can detect is

An optical fibre communication system works on a wavelength of 1.3 \(\mu\)m. The number of subscribers it can feed, if a channel requires 20 kHz are

The resistance of a wire is R ohm. If it is melted and stretched to n times its original length, its new resistance will be

For the given electrical arrangement, what is the value of current I?

The velocity of the proton is one-fourth the velocity of the electron. What is the ratio of the de-Broglie wavelength of an electron to that of a proton?

From the figure describing photoelectric effect, we may infer correctly that

Within the elastic limit, the corresponding stress is known as

A wire is stretched to double of its length. The strain is

The correct arrangement in increasing order of wavelength of X-rays, UV rays, microwave is

Which of the following waves are used to treatment of muscles ache?

Insulators can be charged by which of the following process?

Work done in moving a charge of 25C is 50 J. Calculate potential difference, between two points.

What is the electric field near infinite plane sheet of charge density \(\sigma\) ?

According to Pascal's law, pressure in a fluid at rest is the same at all points, if

The surface tension of a liquid at its boiling point

Kepler's second law of planetary motion corresponds to

A constant potential energy of a satellite is given as
\(\mathrm{PE}=r(\mathrm{KE})\)
whee, PE = potential energy
and KE = kinetic energy.
The value of \(r\) will be

In an adiabatic process with the ratio of two specific heat, \(\gamma=\frac{3}{2}\), pressure is increased by \(\frac{2}{3}\)%, then decrease in the volume will be

For an ideal gas, coefficient of volume expansion is given by

Which of the following is not a green house gas?

The collision of the molecules of an ideal gas is taken as

The average energy associated with a monoatomic molecule is

Carnot cycle of an engine is given below

Total work done by the gas in one cycle is

The motion of a particle of mass \(m\) is described by \(y = ut + g{t^2}\). The force acting on the particle will be

A bar magnet is oscillating in the earth's magnetic field with a period T. What happens to its period and motion, if its mass is quadrupled?

The relative permeability of iron is 6000. Its magnetic susceptibility is

Which graph shows the correct \(v\) - \(x\) graph of a freely falling body?

The displacement \(x\) of a particle varies with time \(t\), \(x=ae^{-pt}+be^{qt}\), where a, b, p and q are positive constant. The velocity of the particle will

The angle of projection with the horizontal in terms of maximum height attained and horizontal range is given by

Two particles of masses \(m_1=m,m_2=2m\) and charges \(q_1=q,q_2=2q\) entered into uniform magnetic field. Find \(F_1/F_2\) (force ratio).

A long solenoid has 20 turns cm\(^{-1}\). The current necessary to produce a magnetic field of 20 mT inside the solenoid is approximately

A constant current flows from A to B as shown in the figure. What is the direction of current in the circle?

Two converging lenses of focal length 20 cm and 40 cm are placed in contact. The effective power of the combination is

The magnifying power of a telescope is 9. When it is adjusted for parallel rays, the distance between the objective and eyepiece is 20 cm. The focal length of lenses are

Newton's second law of rotational motion of a system particles having angular momentum L is given by

Find the logic gate, when both the inputs are high but the output is low and vice-versa.

What is the minimum band-gap of the LED diode?

The function \(y = \log \omega t\) can represent