CognitoQuiz

When we take off clothes in dark, we see a spark and crackling sound. Because - Our body gets rubbed with clothes.  - This produces charges.  - When charges meet, they cause spark and crackling sound.  Charged object Object having electric charge.  Example- Rubbed balloon Electric charges are generated by rubbing.  Types of charges-  (a) Positive charge  (b) Negative charge  Interaction between charges -Like charges repel each other.  -Unlike charges attract each other.  It is a convention to call the charge acquired by a glass rod when it is rubbed with silk as positive.  The another kind of charge is said to be negative.  Static charge  Charge that do not move.  Electric current Movement of charges , is electric current.  Electroscope  A device that test whether an object is charged or not, is called electroscope. 

Good Conductor The substance through which electricity can pass is called good conductor.  Examples - Copper, Aluminum Poor conductor The substance through which electricity can not pass is called poor conductor. Examples - Rubber, plastic etc.  Tester A device that test conductance of a substance, is called tester.  Solutions of acids, bases and salts are generally good conductor.  Chemical effects of Current Chemical reactions (effects) caused when electricity passes through a conducting liquid, is chemical effects of current.  How to recognize chemical reaction - Release of gas - Change of colour of solution - Release of heat - Formation of new substance In battery No. of terminals- 2 (positive and negative)  Positive terminal is also called Anode .  Negative terminal is also called cathode .  Solution  is called electrolyte .  Passing current through a solution What happens when electricity is passed through c

Friction The force that opposes the relative motion between two surfaces in contact, is called friction.  Factors affecting friction Weight of object  Nature of surfaces in contact More the weight of object, more the friction.  More smooth surface experience less friction.  Importance of friction Friction helps in stopping object Friction helps to write, walk,  Friction helps in all activities Friction produces heat.  Harm cause by Friction Sole of shoes wear out.  Machine parts get wear out.  Friction can be increased by making surfaces rough. ( More rough means more interlocking between surfaces which means more friction )  Friction can be decreased by applying lubricant on surfaces.  Friction can be decresed by changing shape of object.  Rolling friction The force that oppose motion of rolling object, is rolling friction.  Sliding friction The force that oppose motion of sliding object, is sliding friction.  Sliding fri

Force   The push or pull of an object, is called force.  Forces are due to interaction between objects.  Force applied on an object in the same direction add to each other.  Force applied on an object in opposite directions substract each other.  The strength of force is measured by its magnitude.  A force can change the state of motion of an object.  Change in state of motion jeans Rest to motion Motion to rest  Increase in speed  Decrease in speed Force on an object may change its shape.  Types of forces   Contact force   The force that can be applied only by touching object,is called contact force.  Non-Contact force   The force that can be applied without touching object,is called contact force.  Muscular force   The force resulting due to action of muscles is called muscular force.  Friction The force that oppose motion of an object.  Magnetic force The force exerted by a magnetic material is called magnetic force.  Like pole repel each other.  Unlike pole attract each other.  Ele

Reaching the Age of Adolescene  Adolescene The period of life, when the body undergoes changes , leading to reproductive maturity, is called adolescene.  Period - age of 11 to age of 19. Also called " teen age ". Because this period covers the teen ages i.e, 13 to 19  Adolescene may begin earlier in girls than boys.  Puberty Period during adolescene, when human body undergoes several changes, is called puberty.  Important change - Boys and girls become capable of reproduction.  Changes at puberty   Increase in height  Change in body shape  Change in voice  Increased activity of sweat and sebaceous glands  Development of sex organs  Reaching mental, intellectual and emotional maturity Changes in Girls   Increase in height Region below the waist becomes wider  Less growth of muscles  Voice becomes high pitched.  Increased activity of sweat and sebaceous glands Ovaries enlarge.  Eggs begin to mature.  Reaching mental, intellectual and emotional maturity Changes in boys   Increa

Reproduction in Animals ·                 Reproduction (Re+Production) Production of living being of own kind, is called reproduction. ·               Importance of reproduction Reproduction ensures continuation of similar kinds of individuals, generation after generation. ·                Modes of reproduction (a) Asexual   reproduction (b) Sexual reproduction ·                 Sexual reproductio       Mode of reproduction where               -Two parents are involved.                -Formation of gametes takes place.               -Fusion of male and female gamete takes place,         Is called sexual reproduction. ·                  Asexual reproduction   Mode of reproduction where               -Single parent is involved.                -Formation of gametes do not takes place.                -Fusion of male and female gamete do not takes place,            Is called asexual reproduction. ·                       Male reproductiv

Cell - Structure and Functions   * Cell - Structural and functional unit of life, is called cell. * Discovery of cell   - Discovered by - Robert Hooke - Used - Thin slice of cork. - Cork - Part of bark of a tree * Egg of a hen represent single cell. * Multicellular organism -Organism made of more than one cells, is called multicellular organism. - Example- Human - Multicellular organism begins life as a single cell. * Unicellular organism - Single celled organism are called unicellular organism. - Example- Amoeba * Shape of cells             Cell                                 Shape        Amoeba, WBC(White Blood Cell)     Irregular shape      Muscle cell                      Spindle shape          RBC                               Spherical      Nerve cell                     Branched shape * Pseudopodia - ( Pseudo - False, Podia - Foots) -Protruding out projections on body of amoeba, is called pseudopodia. -Pseudopodia appear and disappear as