| | | The Atomic Theory |  الثلاثاء سبتمبر 21, 2010 12:01 pm من طرف omar jaber |
Rutherford's gold foil experiment, performed in conjunction with Geiger andMarsden, provided evidence for the nucleus due to the scattering of alphaparticles. The repulsion of some alpha particles suggested that the nucleusis positively charged, containing protons. Further work by Chadwick revealedthe existence of neutrons within the nucleus of the …[/img(591,38):c189]
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| The Motor Principle | | الثلاثاء سبتمبر 21, 2010 11:59 am من طرف omar jaber |
The Motor Principle: when a current-carryingconductor is located in an external magnetic field perpendicular to theconductor, the conductor experiences a force perpendicular to itself and to theexternal magnetic field.
The right-hand rule for force on a conductorcan be used to determine the direction of the force experienced on theconductor: if the …[/img(591,38):2182]
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| AC circuits | | الثلاثاء سبتمبر 21, 2010 11:57 am من طرف omar jaber | 
Direct current ( DC) circuits involve currentflowing in one direction. In alternating current ( AC) circuits,instead of a constant voltage supplied by a battery, the voltage oscillates ina sine wave pattern, varying with time as:V = V 0sin wt
where w is the angular frequencyrelated to the frequency f by:w = 2pf.In a circuit which only involves …[/img(591,38):b380]
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| Ohm's Law ...waves | | الثلاثاء سبتمبر 21, 2010 11:56 am من طرف omar jaber | 
Ohm's Law. The potential difference between any two pointsin a conductor is directly proportional to the current flowing throughit. (This only holds true for an ohmic material. Non-ohmic materialsdo not display a direct relationship.)V = IR
where V is the potential differencemeasured in volts, I is the currentmeasured in amperes and R is the resistance …[/img(591,38):10e0]
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| The Doppler Effect | | الثلاثاء سبتمبر 21, 2010 11:54 am من طرف omar jaber | 
When a source generating waves moves relative to an observer, or whenan observer moves relative to a source, there is an apparent shift infrequency. If the distance between the observer and the source isincreasing, the frequency apparently decreases, whereas the frequencyapparently increases if the distance between the observer and thesource is …
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| Laws of reflection | | الثلاثاء سبتمبر 21, 2010 11:52 am من طرف omar jaber |
A light ray is a stream of light with the smallestpossible cross-sectional area. (Rays are theoretical constructs.) The incident ray is defined as a ray approaching a surface. The point of incidence is where the incident ray strikes a surface. The normal is a construction line drawn perpendicular to the surface at thepoint of incidence. The …[/img(591,38):b2f8]
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| information about waves | | الثلاثاء سبتمبر 21, 2010 11:46 am من طرف omar jaber |
Wave is a transfer of energy, in the form of disturbance through some medium, without translocation of the medium. A wave having a shortduration is called pulse. Waves that vibrate in repeating cyclesillustrate periodic motion or harmonic motion. One complete oscillation is called cycle.
Transverse vibration occurs when vibration of the medium is …[/img(591px,38px):b70c]
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| ميسي أفضل هداف لبرشلونة أوروبياً | | الخميس سبتمبر 16, 2010 3:58 pm من طرف omar jaber | ميسي أفضل هداف لبرشلونة أوروبياً
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| WATER POLLUTIONAND SOCIETY | | الأربعاء سبتمبر 15, 2010 12:09 pm من طرف rami |
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Comprising over 70% of the Earth�s surface, wateris undoubtedly the most …[/img(501,343):956d][/img(253,232):956d]