# Lesson Archives

1. ## Management of Natural Resources

Natural Resources includes total natural environment that support human life and contribute to the production of necessities and comforts to mankind. So natural resources are the coihponents of atmosphere, hydrosphere and lithosphere. Types of Natural Resources: On the basis of abundance and availability, the natural resources are of two types Inexhaustible. Exhaustible. (a) Inexhaustible: These are in […]
2. ## Our Environment

Biodegradable and Non-biodegradable Wastes, Ecosystem, Components of Ecosystem. The environment includes our physical surroundings like air (or atmosphere), water bodies, soil (land and all the organisms such as plants, animals, human beings and micro-organisms like bacteria and fungi (called decomposers). The waste materials produced by the various activities of man £nd animals are poisonous to […]
3. ## Sources of Energy

Sources of Energy: A source of energy is that which is capable of providing enough useful energy at a steady rate over a long period of time. A Good source of energy should be : Safe and convenient to use, For example; energy nuclear can be used only by highly trained engineers with the help of […]
4. ## Magnetic Effects of Electric Current

Magnet: Magnetic field and magnetic field lines, Magnetic field due to a current carrying conductor, Right hand thumb rule, Magnetic field due to current through a circular loop. Magnetic field due to current in a solenoid. Magnet is an object that attracts objects made of iron, cobalt and nickle. Magnet comes to rest in North – […]
5. ## Electricity

Electricity: Electric current, electric circuit, voltage or electric potential, resistance and (Ohm’s law). Electric Current: The flow of electric charge is known as Electric Current, Electric current is carried by moving electrons through a conductor. By convention, electric current flows in the opposite direction to the movement of electrons. Electric Circuit: Electric circuit is a continuous and closed […]
6. ## Probability

Probability: It is the numerical measurement of the degree of certainty. Theoretical probability associated with an event E is defined as “If there are ‘n’ elementary events associated with a random experiment and m of these are favourable to the event E then the probability of occurrence of an event is defined by P(E) as the […]
7. ## Human Eye and Colourful World

Human Eye: working of human eye, Persistence of vision, Power of accommodation of human eye, Defects of vision. The Human Eye: It is a natural optical instrument which is used to see the objects by human beings. It is like a camera which has a lens and screen system. Structure of the Human Eye The various parts […]
8. ## Statistics

MEAN (AVERAGE): Mean [Ungrouped Data] – Mean of n observations, x1, x2, x3 … xn, is MEAN [Grouped Data]: The mean for grouped data can be found by the following three methods: (i) Direct Mean Method: Class Mark = Note: Frequency of a class is centred at its mid-point called class mark. (ii) Assumed Mean Method: In this, an […]
9. ## Surface Areas and Volumes

SURFACE AREA AND VOLUME OF COMBINATIONS Cone on a Cylinder. r = radius of cone & cylinder; h1 = height of cone h2 = height of cylinder Total Surface area = Curved surface area of cone + Curved surface area of cylinder + area of circular base = πrl + 2πrh2 +πr2; Slant height, l = Total Volume […]
10. ## Areas related to Circles

Circumference of a circle = 2πr Area of a circle = πr2 …[where r is the radius of a circle] Area of a semi-circle =πr2 / 2 Area of a circular path or ring: Let ‘R’ and ‘r’ he radii of two circles Then area of shaded part = πR2 – πr2 = π(R2 – r2) = π(R + r)(R […]