6th Standard Physics

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2 PHYSICS: 2 6th Standard Physics Term I Physics is the branch of science that deals with measurement, motion, sound light, electricity, electronics etc. Measurement and motion: Measurement is a process of comparison of an unknown quantity with a standard [accepted] quantity of the same kind. The known constant quantity is called unit. Metre is the unit of length. Kilogram is the unit of mass Minute is the unit of time. Standard Measurement is any measurement that gives the same value for all. The units which Fundamental quantities: are used standard measurement are called Standard units Length, Mass and time are called fundamental quantities, because they cannot be expressed on terms of any other physical quantity. Fundamental units- They are used to measure the fundamental quantities. System International [SI] units: them are. Different parts of the world use different system of units for measuring length,mass and time. Some of 1. FPS system Foot-pound-second 2. CGS system Centimeter, Gram, Second 3. MKS system Metre, kilogram, second To overcome various difficulties, an international system was adopted in This system is called SI units. The SI units of length, Mass, Time is: Physical quantity SI units Symbol 1.Length Metre M 2. Mass Kilogram Kg 3.Time Second S

3 Measurement of Length: Def : The distance between two points is called length. SI unit: Meter Multiples and submultiples of length: Physical quantity SI unit Multiples Submultiples Length Metre Kilometre Millimetre, Centimetre Multiples: Larger distances, such as the distance between two places are expressed in kilograms. Submultiples: Smaller length such as length of a pencil, pen nib is expressed in centimeter. 1 metre = 1000 millimeters 1 metre = 100 centimeters 1 kilometre = 1000 metres Measurement of Mass: Def: The mass of a body is the amount of matter contained on it. SI unit: kilogram. Multiples and submultiples of mass: Physical quantity SI unit Multiples Submultiples Mass Kilogram Quintal, metric tone Gram, milligram Multiples : For measuring larger quantities we use units such as quintal, metric, ton. Submultiples: For measuring smaller quantities we use units such as gram and milligram. 1 gram = 1000 milligram 1 kilogram = 1000 grams 1 quintal = 100 kilograms 1 metric ton = 1000 kilograms Measurement of time: Def :Time is the interval between two events. SI unit: second. 3

4 Multiples and submultiples of time: Physical quantity SI unit Multiples Sub multiples Time Second Minute, hour, day, week, month, year Millisecond, microsecond Multiples : Larger time intervals are expressed in minute, hour, day, week, month, and year. Submultiples: Any time interval less than 1 second is expressed in millisecond, microsecond etc. 1 meter = 1000 millimeters 1metre = 100 centimeters 1 kilometer = 1000 meters. FACTS : 1. The length of the largest Sea animal, blue whale measures 30 approximately 2. Mass of the Sun = 1.99 * kilogram 3. Mass of the Earth = 5.98 * kilogram 4. Mass of the Sun is 3, 20,000 times heavier than the earth. MOTION: Def : Motion is defined as the change of position of an object with respect to time. If an object does not change its position with respect to time, it is said to be Stationary or at rest. Rest and motion are relative Types of Motion: 1. Linear motion: When an object moves along a straight line, it s said to be in linear motion. Eg : Motion of a lift. 4

5 2. Circular motion: If an object moves along a circular path, it is said be in circular motion. Eg : A point marked on the blade of the fan. 3. Rotational motion: If a body revolves about an axis, it is said to be in rotational motion. Eg : Motion of a fan. 4. Periodic motion: If an object repeats the same type of motion at regular intervals of time it is said to be periodic motion. Eg : Motion of a child in a swing. 5. Random motion: When an object moves at different speeds and in different direction, it is said to be in random motion. Eg : A Fish swimming in a tank. MAGNETISM: A shepherd named magnets of a town magnesia in Asia Minor discovered a rocks that had attracting property. As it was discovered by magnets they named that rock as magnet and also magnetite. Magnetite s are natural magnets. They are also called as magnetic stones. They are also called as leading Stones (or) lodestones because when a magnet is freely suspended, it always comes to rest in north south direction. Man made magnets are called as artificial magnets. Some shapes are bar mag net, horse shoe magnet, Ring magnet. Magnetic and non magnetic substances: Magnet Magnetic Non magnetic Substances that are attracted by magnet are called magnetic substances. Example: Iron, cobalt, nickel Substances that do not get attracted by magnetic are called non magnetic substances. Example: Paper, plastic. 5

6 Poles: Def : The ends of a magnet have the strongest magnetic force. North and South Poles: North seeking pole is called north pole. South seeking pole is called south pole Magnetic compass has been designed by using this directive property of the magnet. Magnetic compass: The magnetic needle is pivoted at the centre of a circular disc.this magnetic needle always rests in north south direction.so with this magnetic compass we can find out different directions. Attraction and repulsion: 1.Like poles repal each other. N S S N 2. Unlike poles attract each other. N S N S Magnets lose their properties if they are 1. Heated 2. Dropped from a height 3. Hit with a hammer. They also lose their properties when they are kept near the cassettes, mobiles, television compact disk & the computer. Facts: 1. Electromagnets are used in giant wheels 2. In 1600, English scientist William Gilbert proposed that earth behaves like a giant magnet. 3. Electromagnet train is also called as suspension train. In France it is called flying train. 4. Technology used is the property of magnetic attraction and repulsion. 6

7 Standard 6 Terms II TYPES OF ENERGY: Energy: Def : We define energy as the capacity (or) ability to do work. Unit of energy: joule Types: 1. Mechanical Energy: Mechanical Energy is the energy possessed by an object due to its move mint (or) position. Potential Energy Mechanical Energy Kinetic Energy Potential Energy: Def : The energy possessed by an object by virtue of its position (or) configuration is called potential energy. Eg : Things like a composed spring (or) a stretched rubber band have potential energy due to its configuration. Kinetic energy: Def : The energy possessed by a body by virtue of its motion is called kinetic energy. Eg : A flowing river, a moving bus. Potential energy and kinetic energy are inter convertiable. This property is used to generate electricity in hydro electric power stations. Uses: 1. Mechanical energy can bring a moving body to rest (or) can make a body at rest to move. 2. Using wind energy, we can generate electricity through windmills. 2.Chemical Energy: Def : Energy that is stored in the bonds of chemical compounds is called chemical energy. Eg :Chemical energy is released during a chemical reaction often in the form of heat and light. Uses: 1. The chemical energy stored in the food of plants and animals is used for their growth and function 2. A battery (or) an electric cell convertschemical energy intoelectrical energy 3. While using fuels, chemical energy is converted into heat energy and light energy. 7

8 3. Electrical Energy: In an electric bulb, electrical energy is converted into light energy and in an electric fan; electrical energy is converted into mechanical energy. In a windmill the wind energy is converted into electrical energy. Uses: 1. In industries, electrical energy is used to operate machines and is also used in telecommunication. 2. Electrical energy is used to run electric trains. 4. Heat Energy: The primary source of heat energy is Sun, The chemical energy stored in wood, kerosene and LPG is converted into heat energy. Heat is produced due to friction and chemical reaction. Uses: 1.Due to heat energy we get rain. 2.In a thermal power station, of electricity is generated from the heat energy obtained by burning coal. 5. Solar Energy: Def : The energy that is obtained from the sun is called solar energy. Uses: 1.Solar energy is directly used in solar heater, solar cooker etc. 2.Solar cells are used in artificial satellites, watches, calculators and are used to operate solar vehicles. Law of conservation of energy: Energy can neither be created nor be destroyed, but can be transformed from one form in to another. This is called law of conservation of energy. Facts: 1. Heat is a form of energy jams joule [The unit of energy [joule] is named after him] 2.In matter and Bhavanisagar, electricity is generated using hydroelectric power. Example for energy conversion: Electrical energy kinetic energy + sound energy + [to lift water] [To operate the electric Motor] heat energy 8

9 Standard 6 Term III Light: We need Light to see objects. Source of light: The objects that give light are called as source of light. Source of light are of two types. Sources of light Nature Artificial 1. Nature: The Sun is the primary and natural source of light. E.g: Sun, Fire flies, jelly fish. 2. Artificial: The man made objects also produce light. They are artificial sources of light. E.g: oil lamp, decorative lamp. Luminous Bodies and Non luminous bodies: Bodies that emit light on their own are called luminous bodies. Objects that donot emit light on their own are called non luminous bodies Propagation of light: The property of Rectilinear propagation of light confirms that light travels only in a Straight line. Transparent, Translucent and opaque objects: The objects that allow light to pass through them are called as transparent objects. The objects which allow the light to pass through them partially are called translucent objects. The objects which do not allow light pass through them are called opaque objects. Shadows: When certain objects are placed in front of sunlight or torch light a shadow is formed behind the object. Properties of shadow: 1. Shadow is always formed on the opposite side of the light source. 2. It only shows the shape (or) outline of the object. 9

10 3. A shadow cast by an intense beam of light is dark. 4. A shadow is always black in color. 5. The size of the shadow varies depending on the distance between the object and the object and the source of light. 6. Source of object and the shadow will always lie in a straight line. Reflection of light and plane mirror: Def : When a beam of light falls on a smooth shining surfaces, it bounces back into the same medium [solid, liquid (or) gas] this phenomenon is called reflection. Plane mirrors: What we see on the mirror is our own reflection. This is called reflection When the reflected rays from the mirror reach our eyes we are able to the see the image of our face in the mirror. This is called plane mirror Lunar Eclipse :(Eclipse of the moon) When the earth comes between the sun and the moon, lunar eclipse occurs. This happens on a full moon day. The Sun source The Earth - opaque object The Moon - screen When the shadow of earth falls on the moon, the moon is hidden. This is called Lunar Eclipse. Solar Eclipse: [Eclipse of the Sun] When the moon comes between the sun and the earth, solar eclipse occurs.this happens on a new moon day. The Sun - source of light The Moon - opaque object The Earth - screen When the shadow of the moon falls on the Earth, the Sun is hidden. This is called as solar Eclipse. 10

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