A generator produces a voltage that is given by V=240 sin 120t where t is in sec. The frequency and r.m.s. voltage are
Suppose an electron is attracted towards the origin by a force k/r where 'k' is a constant and 'r' is the distance of the electron from the origin . By applying Bohr model to this system , the radius of the nth orbital of the electron is found to be 'r'n and the kinetic energy of the electron to be Tn . Then which of the following is true ?
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A parallel plate capacitor is charged. If the plates are pulled apart
A charged particle is released from rest in a region of steady and uniform electric and magnetic fields which are parallel to each other. The particle will move in a
A certain piece of silver of given mass is to be made like a wire. Which of the following combinations of length (L) and the area of cross-section (A) will lead to the smallest resistance
A 2kg ball moving at 24 ms-1 undergoes inelastic head-on collision with a 4 kg ball moving in the opposite direction at 48 ms-1. If the coefficient of restitution is 2/3, their velocities in ms-1 after impact are
If momentum of a particle is doubled, then its de-Broglie's wavelength will
Quantam nature of light is explained by which of the following phenomenon
When yellow light is incident on a surface, no electrons are emitted while green light can emit. If red light is incident on the surface, then
The coil of a dynamo is rotating in a magnetic field. The developed induced e.m.f. changes and the number of magnetic lines of force also changes. The phenomenon can be correctly described as
In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor, when the energy is stored equally between the electric and magnetic field is
What is the value of inductance L for which the current is a maximum in series LCR circuit with C = 10 μF and ω = 1000s−1 ?
The maximum distance upto which TV transmission from a TV tower of height h can be received is propotional to
Which of the following represents the emf of a battery?
A parallel plate capacitor is made by stacking n equally spaced plates connected alternatively. If capacitance between any two adjacent plates is C, then the resultant capacitance is
A particle of mass m is moving in a horizontal circle of radius r under a centripetal force equal to - K/r2, where K is a constant. The total energy of the particle is
If the unit of force and length be each increased by four times, then the unit of energy is increased by
At temprature T, the poewr radiated by a body is Q watts. At the temprature 3T the power radiated by it will be
A piece of fuse wire melts when a current of 15 ampere flows through it. With this current, if it dissipates 22.5 W, the resistance of fuse wire will be
A bar magnet of pole strength 2 A-m is kept in a magnetic field of induction 4 x 10−5 wbm−2 such that the axis of the magnet makes an angle 30º with the direction of the field. The couple acting on the magnet is found to be 80 10−7N-m . Then the distance between the poles of the magnet is
A bar magnet of magnetic moment M and length L is cut into two equal parts each of length L/2. The magnetic moment of each part will be
How much force is required to produce an elongation of 0.2% in the length of a brass wire of diameter 0.6 mm? (Take Young's modulus for brass = 0.9x1011 N-m⁻2)
A body is imparted motion rest to move in a straight line. If it is then obstructed by an opposite force, then
Radioactive disintegration differs from a chemical change in being
Two springs of constants k₁ and k₂, have equal highest velocities, when executing SHM. Then, the ratio of their amplitudes (given their masses are eqaul) will be
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): Electrical resistivity of typical insulator (≃ 1014Ω-m) is about 1022 times that of metal (≃ 10-8Ω-m) while in case of heat it is only about 103 (as KAg ≃ 400 W/mk while Kglass ≃ 1 W/mk)
Reason(R): In electrical conduction only free electrons take part while in thermal conduction both lattice and free electrons contribute.
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): When light goes from a medium of refraction index 1.5 to a medium of refraction index , 1.6, its speed decreases by 1.875 x 108 m/s.
Reason(R): Refraction index
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A): When net force is perpendicular to direction of velocity, it just changes its direction and not magnitude.
Reason (R): This results in uniform circular motion.
In the following question, a Statement of Assertion (A) is given followed by a corresponding Reason (R) just below it. Read the Statements carefully and mark the correct answer-
Assertion(A):A certain radioactive substance has a half life period of 30 days. Its disintegration is 0.0231 day.
Reason(R):Decay constant varies inversely as half life.