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There are two types of charges: positive charge, i.e., the charge that a glass rod acquires when rubbed with silk and negative charge, i.e., the charge which an ebonite rod acquires when rubbed with flannel.

Magnet is a naturally occurring or artificially designed material which has a peculiar property of attracting some materials like iron, nickel and cobalt, called magnetic materials.

Sound is the form of energy which gives the sensation of hearing. It travels in the form of waves.

The earth came into existence 4-5 billion years ago and life originated around 3.4 billion years ago. In these many years, approximately 15 million different kinds of organisms have evolved. The wide variety of organisms is termed biodiversity.

Earth is the only planet in our solar system which sustains life. But earth was not the same as it is today. It was a ball of gases when it was first formed about 4.5 billion years ago. Earth cooled and chemicals of life were synthesized in water - chemical evolution.

Cell is the structural and functional unit of life. A typical cell includes a cell membrane, cytoplasm and genetic material either within the nucleus or in the cytoplasm.

Life Processes such as Nutrition, Respiration, Circulation and Excretion are necessary for the survival of living beings. Energy is needed for running life processes.

Blood vessels carry oxygen from alveoli to tissues. Cells of tissues take up the oxygen. In the mitochondria of the cells, oxygen acts upon glucose to yield energy and release carbon dioxide. This is called cellular respiration.

Blood transports food and oxygen to all the cells of the body. It is made of fluid plasma and cells. Plasma which transports glucose, enzymes and hormones to cells, carries waste material from liver to kidneys for removal.

Excretion is the removal of harmful wastes like urea by kidneys, sweat from skin and CO₂ by Lungs.

Nervous system (NS) and endocrine system together ensure that all the parts of the body work in a controlled and coordinated manner.

Features passed down from one generation to the other is Heredity or Inheritance. Genes control heredity. Differences in features of individuals of the same species is variation.

Air is a mixture of different gases. It contains oxygen, Nitrogen, Argon, Carbon dioxide and traces of some inert gases. It also contains water vapour.

Water is the abundant natural resource available. Although sea water is the largest natural source of water, it is unfit for domestic use and drinking. Water is essential for survival of all living beings.

Elements are broadly classified as metals nonmetals. Metals can be distinguished from non-metal on the basis of their physical properties like malleability ductility, lusture.

Diamond has a three-dimensional network of covalently bonded carbon atom. It is hard and colourless. It has high melting and boiling point and is a good conductor of heat but poor conductor of electricity.

In an ecosystem, living organisms interact among themselves and also with the surroundings continuously and yet maintain a balance. Ecosystem is divided into two basic categories namely terrestrial and aquatic.

Mendeleev’s Periodic Table was based on atomic masses. Modern Periodic Table arranges the elements in the order of their atomic numbers in seven horizontal rows (periods) and eighteen vertical columns (groups or families).

Atoms are the building blocks of elements. They are the smallest parts of an element that chemically react. The first atomic theory, proposed by John Dalton in 1808, regarded atom as the ultimate indivisible particle of matter.

Current through a given area of a conductor is the net charge passing per unit time through the area.

Electrostatic force is a conservative force. Work done by an external force (equal and opposite to the electrostatic force) in bringing a charge q from a point R to a point P is q(V_P - V_R), which is the difference in potential energy of charge q between the final and initial points.

Electric and magnetic forces determine the properties of atoms, molecules and bulk matter.

From simple experiments on frictional electricity, one can infer that there are two types of charges in nature; and that like charges repel and unlike charges attract. By convention, the charge on a glass rod rubbed with silk is positive; that on a plastic rod rubbed with fur is then negative.

Semiconductors are the basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc.

Lattice structure and the atomic structure of constituent elements decide whether a particular material will be insulator, metal or semiconductor.

Environmental problems may arise due to natural disasters or due to human activities.

India is a large country. India is the seventh largest country of the world. It extends from the state of Jammu and Kashmir in the North to the state of Tamil Nadu in the South; from the state of Arunachal Pradesh in the east to the state of Gujarat in the west.

India has monsoon type of climate. The word monsoon refers to the seasonal reversal of the wind direction in a year. Due to this, India has four prominent seasons - cold weather season, hot weather season, advancing southwest monsoon season and post or retreating monsoon season.

Alkyl or Aryl halides may be classified as mono, di, or polyhalogen (tri-, tetra-, etc.) compounds depending on whether they contain one, two or more halogen atoms in their structures.

The chemistry of coordination compounds is an important and challenging area of modern inorganic chemistry. During the last fifty years, advances in this area, have provided development of new concepts and models of bonding and molecular structure, novel breakthroughs in chemical industry and vital insights into the functioning of critical components of biological systems.

The d-block consisting of Groups 3-12 occupies the large middle section of the periodic table. In these elements the inner d orbitals are progressively filled. The f-block is placed outside at the bottom of the periodic table and in the elements of this block, 4f and 5f orbitals are progressively filled.

Chemical kinetics is the study of chemical reactions with respect to reaction rates, effect of various variables, rearrangement of atoms and formation of intermediates.

Chemistry, as we understand it today is not a very old discipline. People in ancient India, already had the knowledge of many scientific phenomenon much before the advent of modern science. They applied the knowledge in various walks of life.

Hydrocarbons are the compounds of carbon and hydrogen only. Hydrocarbons are mainly obtained from coal and petroleum, which are the major sources of energy.

Organic compounds are formed due to covalent bonding. The nature of the covalent bonding in organic compounds can be described in terms of orbitals hybridisation concept, according to which carbon can have sp³, sp² and sp hybridised orbitals.

Redox reactions form an important class of reactions in which oxidation and reduction occur simultaneously.

When the number of molecules leaving the liquid to vapour equals the number of molecules returning to the liquid from vapour, equilibrium is said to be attained and is dynamic in nature.

Thermodynamics deals with energy changes in chemical or physical processes and enables us to study these changes quantitatively and to make useful predictions. For these purposes, we divide the universe into the system and the surroundings.

Kössel’s first insight into the mechanism of formation of electropositive and electronegative ions related the process to the attainment of noble gas configurations by the respective ions. Electrostatic attraction between ions is the cause for their stability. This gives the concept of electrovalency.

An atom has a nucleus. The nucleus is positively charged. The radius of the nucleus is smaller than the radius of an atom by a factor of 10⁴. More than 99.9% mass of the atom is concentrated in the nucleus.

Atom, as a whole, is electrically neutral and therefore contains equal amount of positive and negative charges.

In Thomson’s model, an atom is a spherical cloud of positive charges with electrons embedded in it.

The minimum energy needed by an electron to come out from a metal surface is called the work function of the metal. Energy (greater than the work function (φ_ο) required for electron emission from the metal surface can be supplied by suitably heating or applying strong electric field or irradiating it by light of suitable frequency.

Huygens’ principle tells us that each point on a wavefront is a source of secondary waves, which add up to give the wavefront at a later time.

Reflection is governed by the equation ∠i = ∠r′ and refraction by the Snell’s law, sini/sinr = n, where the incident ray, reflected ray, refracted ray and normal lie in the same plane.

Maxwell found an inconsistency in the Ampere’s law and suggested the existence of an additional current, called displacement current, to remove this inconsistency. This displacement current is due to time-varying electric field.

An alternating voltage v = v_m sin ωt applied to a resistor R drives a current i = i_m sin ωt in the resistor, i_m = v_m/R. The current is in phase with the applied voltage.

The magnetic flux through a surface of area A placed in a uniform magnetic field B is defined as, Φ_B = B.A = BA cos θ where θ is the angle between B and A.

The science of magnetism is old. It has been known since ancient times that magnetic materials tend to point in the north-south direction; like magnetic poles repel and unlike ones attract; and cutting a bar magnet in two leads to two smaller magnets. Magnetic poles cannot be isolated.

The total force on a charge q moving with velocity v in the presence of magnetic and electric fields B and E, respectively is called the Lorentz force.

The property of an object by virtue of which it cannot change its state of uniform motion along a straight line or rest on its own is called as inertia. It is the measure of the mass of a body.

Motion in a plane is the motion in two dimensions, for instance, projectile motion, circular motion and so on.

A body is said to be in motion if it changes its position with respect to time.