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    عدد المساهمات : 114
    نقاط : 55181
    تاريخ التسجيل : 22/04/2009
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    مُساهمة من طرف atwa الأربعاء مارس 17, 2010 2:15 pm

    The sound
    The sound: it is external factor that affect the ears causes the sensation
    Of hearing.
    * Sound produce due to vibration of object.
    The Sources of sound:
    1-human speech
    2- Animal by communication
    3- Plants
    4- Natural phenomena.
    5- Different object as TV, radio

    The sound properties
    1- Sound travels in form of spherical waves
    Its center is the vibrated body.
    2- Sound travels through solid, liquid And gases
    3- Sound waves move in form of compression And rarefaction.
    4- Astronauts use wire less devices to talk
    On the Moon Due to absent of medium
    5- Sound doesn’t travel through vacuum (Space)
    Because it need medium.

    Noise pollution
    Noise: it is any loud sound annoy us
    The source of noise pollution:
    1- Loud speaker 2- factories 3- car horns
    4- Metallic work shops 5- aero planes
    The effect of noise pollution:
    1- difficulty of talking
    2- complete or partly deafness
    3- inability to sleep
    4- reduce production
    5- nervous system stress

    The light
    Light: it is external factors that affect the eyes causes Sensation of vision.
    *Al – Hassan Ibn Al haitham: is the first Arabic scientist who explain
    The vision occurs due to falling of Light On object and reflects
    To the eye causing the vision.
    Source of light:
    1-natural sources: as sun and stars
    2-Artificial sources:
    as electric lamp – Kerosene lamp – candle – fire – torch.
    The properties of light
    1-light travel in straight line
    *the image inverted when light passes through narrow hole
    *formation of shadow due to passing light in straight line
    2-Light reflect: light reflect when it falls on plane mirror.
    3-light refract: light refract when it pass from transparent Medium to another transparent medium.
    4-Light analysis and form spectrum colour.
    * The light splits into seven colours called spectrum colour.
    Which are: red – orange – yellow- green – blue –indigo -Violet
    *rain bow: it appears in the sky after rain fall due to analysis of light.
    What are the properties of light ?









    The Heat
    . Heat: It is a form of energy that causes the sensation of heat or coldness
    *heat transfer from hot body to cold body
    Example: heat transfer from a cub of tea to your hand
    *Heat transfer from your hand to a piece of ice.
    *the sun is the main source of heat on the earth surface.
    Source of heat:
    1-friction الاحتكاك : generate heat
    2-Burningالاشغال :generate heat
    3-Hammeringالطرق generate heat
    4-Passing electric current in wire مرور تيار كهربى فى سلك
    * through electricity .
    The importance of heat
    1-for cooking
    2-necessary for our body
    3- evaporation
    4- melting














    Method of transfer heat
    1- Conduction: It is the transfer of heat through solids from the part of higher temperature to that of lower temperature. by conduction
    * the molecule of solid substance doesn’t transfer .
    Example: heat transfer through a bar of iron or spoon.
    2- Convection: It is the transfer of heat through liquids and gases from the part of higher temperature to that of lower temperature by the movement of the molecules of substance by convection.
    Example : heat transfer through glass of water
    * the movement of saw dust from down to up .
    3- Radiation: It is a way by which the heat is transferred through gases and space by radiation.
    Example : the sun rays transfer to the earth by radiation
    • heat transfer from heater by convection and radiation .




    The effect of heat on solid, liquid and gases
    Solid: expand by heat and contract by cooling
    Example : ring and ball
    Expand : increase in size of the body .
    Contract : decrease in size of body

    Application on expand solid
    1-not stretching electric cables to prevent cutting it when it contract in winter

    2-leaving space between section of railway tracks To prevent them from
    Bending and buckling
    3-leave space in frame of bridge
    to prevent them from collapsing .
    *Liquid expand by heating and contract by cooling.
    -we measure the temperature by using thermometer
    -the idea which thermometer made is expanding liquid by heating and contracting them by cooling .
    The clinical thermometer: it is a device used to measure the temperature of patient.
    * Its graduation from 35 C0 to 42 C0
    * It consists of: graduated glass, capillary tube and glass Bulb
    *There is constriction in clinical thermometer to prevent mercury to return to the bulb.
    The Celsius thermometer: it used to measure the temperature of liquid .
    -its scale begins from zero to 100 C0or 200 C0
    Method measure temperature of patient.
    1- Sterilize thermometer.
    2- shake thermometer to force mercury to bulb
    3- put thermometer under tongue one minute
    4- read it
    5- sterilize it again

    Heat conductors and heat insulators
    Heat conductors : they are materials that are
    Good conductor to heat .
    Examples : iron – copper – silver – Aluminium
    *heat conductors are used in making cooking pots and tea boilers

    Heat insulators : they are materials that are bad Conductors to heat .

    Examples : wood – plastic – glass – clothes
    heat insulators are used in making hands of cooking pots and hands of tea boilers – clothe























    The electric current
    The electric current: it is a flow of electric charge
    That path from one end of wire to the other.

    The electric circuit: it is a closed path through which
    Electric charges pass making complete cycle.

    The components of electric circuit:
    1- dry cell ( battery )
    2- lamp
    3- closed key ( switch )
    4- open switch

    Sources of electric current
    1- dry cell ( battery )
    2- Electric generator (dynamo) .

    The dry cell : it change chemical energy to electric energy
    The dry cell consists of
    1- negative pole : consists of Zinc case ( - )
    2- positive pole : consists of Carbon rod
    Surrounding by manganese dioxide powder ( )
    3- moist paste ( electrolyte ) : consists of
    Ionized salts from ammonium chloride, zinc chloride and starch.
    *Electrolyte connects between the two poles.
    *Dry cell damage if it left long time because it loses its moisture. And become dry.
    *Dry cell damage if it used along time because it's chemical components weak and stops.
    *Dry cell change chemical energy to electric energy.
    *Dry cell used in children toys, radio, watch, torch.



    Use of electricity at home
    • light bulb : change electric energy into light and heat energy .
    • the light bulb consists of :
    1-glass bulb : it is made of glass
    • the glass bulb filled with inert gases to prevent burning the filament of bulb
    2-The filament: it is made of tungsten wire which has high melting point.
    3-two thick copper wire
    4-two piece of lead fixed on base

    The electric iron

    The electric iron consists of :
    1- heat element : it made of nichrome ( nickel chrome )
    * the heat element put between mica sheet ( flak )
    To insulate it from iron body

    2- iron body : it is flat metal and plastic hand

    3- the thermostat : it called regulator or controller
    * it regulate the temperature of clothes according to type of cloth
    * stop electric current from heat element .











    The Fuse

    The fuse : it is a device protect appliances from damage and homes from fire .
    • the fuse used in domestic electrical equipment as Tv , radio ……
    • the importance of fuse : protecting applaiances from damage that when current increase above than normal .
    • when uncovered parts of connecting wire touch each other the wire become hot and cause electric shock .
    • the structure of fuse :

    1- a piece of ceramic ( porcelain )

    2- two cracked copper slide

    3- thin wire of lead


    safe use electric for personal .
    1- don’t touch uncover parts
    2- don’t put your hand inside radio or television when it plugged in .don't put metal in source of electric .
    Safe for home and appliances.
    1- Unplugged appliances which shut off.
    2- sure that appliances switched off before plugged
    3- replace damage wire with new ones .
    4- before replace fuse find out the reason for damage
    to avoid repeating the same problem .

      الوقت/التاريخ الآن هو الأحد أبريل 28, 2024 3:58 pm