A circular coil carrying a current I has radius R and number of turns N. If all the three, i.e. the current
I, radius R and number of turns N are doubled, then, the magnetic field at its centre becomes:
(a) Double
(b) Half
(c) Four times
(d) One fourth
Concept: Magnetic Force
Name a material which is used in making control rods in a nuclear reactor.
Concept: Atomic Masses and Composition of Nucleus
Write one balanced equation to show Emission of `beta^-` (i.e. a negative beta particle)
Concept: Atomic Masses and Composition of Nucleus
An emf of 2V is induced in a coil when the current in it is changed from 0A to 10A in 0·40 sec. Find the coefficient of self-inductance of the coil.
Concept: Electromagnetic Induction
Explain the term hysteresis
Concept: Magnetic Force
Obtain an expression for magnetic flux density B at the centre of a circular coil of radius R, having N turns and carrying a current I
Concept: Magnetic Force
With the help of a suitable example and an equation, explain the term pair production.
Concept: Atomic Masses and Composition of Nucleus
With what type of source of light are cylindrical wave fronts associated?
Concept: Huygens Principle
A converging lens of focal length 40 cm is kept in contact with a diverging lens of focal length 30 cm. Find the focal length of the combination .
Concept: Reflection of Light by Spherical Mirrors
How can the spherical aberration produced by a lens be minimized?
Concept: Reflection of Light by Spherical Mirrors
Two thin lenses having optical powers of -10D and+ 6D are placed in contact with each other. The focal length of the combination is:
Concept: Reflection of Light by Spherical Mirrors
The total energy of an electron in the ground state of the hydrogen atom is -13·6 eV. Its total energy, when a hydrogen atom is in the first excited state, is:
Concept: Alpha-particle Scattering and Rutherford’S Nuclear Model of Atom
Write the expression for the Lorentz force F in vector form.
Concept: Magnetic Force
A coil has a self-inductance of 0·05 Henry. Find the magnitude of the emf induced in it when the current flowing through it is changing at the rate of 100 As-1.
Concept: Electromagnetic Induction
PQ is a long straight conductor carrying a current of 3A as shown in Figure below. An electron moves with a velocity of 2 x 107 ms-1 parallel to it. Find the force acting on the electron.
Concept: Magnetic Force
Define Curie temperature.
Concept: Current Loop as a Magnetic Dipole and Its Magnetic Dipole Moment
If magnetic susceptibility of a certain magnetic material is 0 0001, find its relative permeability.
Concept: Current Loop as a Magnetic Dipole and Its Magnetic Dipole Moment
State how the focal length of a glass lens (Refractive Index 1.5) changes when it is completely immersed in:
(i) Water (Refractive Index 1.33)
(ii) A liquid (Refractive Index 1.65)
Concept: Reflection of Light by Spherical Mirrors
An object is kept on the principal axis of a concave mirror of focal length 10 cm. at a distance of 15
cm from its pole. The image formed by the mirror is:
(a) Virtual and magnified
(b) Virtual and diminished
(c) Real and magnified
(d) Real and diminished
Concept: Ray Optics - Mirror Formula
In Bohr’s model of the hydrogen atom, the radius of the first orbit of an electron is r0 . Then, the radius of the third orbit is:
a) `r_0/9`
b) `r_0`
c) `3r_0`
d) `9r_0`
Concept: Bohr'S Model for Hydrogen Atom