CBSE Class 12 Sample Papers, Syllabus, Test Papers & NCERT Solutions

1. Metals They possess very low resistivity or high conductivity. ρ ~ 10-2.10-8 Ωm, σ ~102. 108 Sm-1 2. Semiconductors They have resistivity or conductivity intermediate to metals and insulators. ρ ~ 10-5. 106 Ωm, σ ~ 10+5 .10-6 Sm-1 Types of Semiconductors Types of semiconductors are given below: (i) Elements Semiconductors These semiconductors are available in natural form, e.g. silicon and germanium. […]

1. In every atom, the positive charge and mass are densely concentrated at the centre of the atom forming its nucleus. More than 99.9% mass of the atom is concentrated in the nucleus. 2. Atomic Mass Unit (amu) The unit to express atomic masses is called atomic mass unit. Atomic mass unit is defined as 1/12 th […]

1. All elements consists of very small invisible particles, called atom. Every atom is a sphere of radius of the order of 10-10 m, in which entire mass is uniformly distributed and negative charged electrons revolve around the nucleus. 2. Experimental arrangement for α-scattering experiment and trajectory followed by α -particles 3. Impact parameter perpendicular distance of the velocity […]

1. Photoelectric Effect The phenomenon of emission of photoelectron from the surface of metal, when a light beam of suitable frequency is incident on it, is called photoelectric effect. The emitted electrons are called photoelectrons and the current so produced is called photoelectric current. Hertz’ Observation The phenomenon of photo electric emission was discovered in 1887 by […]

1. Wave Optics Describes the connection between waves and rays of light. According to wave theory of light, light is a form of energy which travels through a medium in the form of transverse wave. 2. Wave front The locus of all those particles which are vibrating in the same phase at any instant is called wave […]

1. Ray Optics or Geometrical Optics In this optics, the light is considered as a ray which travels in a straight line. It states that for each and every object, there is an image. 2. Reflection Reflection is the phenomenon of changing the path of light without any change in the medium. 3. Reflection of Light The returning […]

1. Displacement Current The current which comes into play m the region in which the electric field and the electric flux is changing with time. It is given by 2. Need for Displacement Current Ampere’s circuital law for conduction current during charging of a capacitor was found inconsistent. Therefore, Maxwell modified Ampere’s circuital law. 3. The displacement current […]

1. Alternating Current (AC) It is the current which varies in both magnitude as well as direction alternatively and periodically. I = I0 sin ωt or I = I0 cosωt where, I0 = peak value or maximum value of AC. 2. Effective Value or rms Value of AC It is defined as the value of AC over a complete cycle […]

1. Magnetic Flux The magnetic flux linked with any surface is equal to total number of magnetic lines of force passing normally through it. It is a scalar quantity. 2. The phenomenon of generation of current or emf by changing the magnetic flux is known as Electromagnetic Induction EMI). 3. Faraday’s Law of Electromagnetic Induction First Law Whenever […]

1. The magnetic dipole moment of a magnetic dipole is given by M = m × 2I where, m is pole strength and 2I is dipole length directed from S to N. The SI unit of magnetic dipole moment is A-m2 or J/T. It is a vector quantity and its direction is from South pole to North […]

1. The space in the surroundings of a magnet or a current-carrying conductor in which its magnetic influence can be experienced is called magnetic field. Its SI unit is Tesla (T). 2. Oersted experimentally demonstrated that the current-carrying conductor produces magnetic field around it. When key K is closed, then deflection occurs in the compass needle and […]

1. The directed rate of flow of electric charge through any cross-section of a conductor is known as electric current. If ∆Q charge flows in time ∆t, then current at any time t is NOTE: Current is a scalar quantity. I is in the direction of flow of positive charge and opposite to the direction of flow […]

1. Electrostatic Potential The electrostatic potential at any point in an electric field is equal to the amount of work done per unit positive test charge or in bringing the unit positive test charge from infinite to that point, against the electrostatic force without acceleration. NOTE: Electrostatic potential is a state dependent function as electrostatic forces are […]

1. Electric Charge Charge is the property associated with matter due to which it produces and experiences electric and magnetic effect. 2. Conductors and Insulators Those substances which readily allow the passage of electricity through them are called conductors, e.g. metals, the earth and those substances which offer high resistance to the passage of electricity are called […]