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...

Atoms Class 12 Notes Chapter 12 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....

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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,...

• Waves Wave is a form of disturbance which travels through a material medium due to the repeated f periodic motion of the particles of the medium about their mean positions without any actual transportation of matter. • Characteristics of wave The characteristics of...

• Periodic Motion Motions, processes or phenomena, which repeat themselves at regular intervals, are called periodic. • Oscillatory Motion The motion of a body is said to be oscillatory motion if it moves to and fro about a fixed point after regular intervals of time....

• The kinetic theory was developed in the nineteenth century by Maxwell, Boltzman and others. Kinetic theory explains the behaviour of gases based on the idea that the gas consists of rapidly moving atoms or molecules. • Ideal Gas An ideal gas or a perfect gas is that...

The branch of physics which deals with the study of transformation of heat into other forms of energy and vice-versa is called thermodynamics. Thermodynamics is a macroscopic science. It deals with bulk systems and does not go into the molecular constitution of...

• Heat is the form of energy transferred between two (or more) systems or a system and its surroundings by virtue of temperature difference. The SI unit of heat energy transferred is expressed in joule (J). In CGS system, unit of heat is calorie and kilocalorie...

Fluids are the sustances which can flow e.g., liquids and gases. It does not possess definite shape. • When an object is submerged in a liquid at rest, the fluid exerts a force on its surface normally. It is called thrust of the liquid. • Pressure The thrust...

• Inter molecular Force In a solid, atoms and molecules are arranged in such a way that each molecule is acted upon by the forces due to the neighbouring molecules. These forces are known as inter molecular forces. • Elasticity The property of the body to regain its...