فيزياء أول ثانوي جيل 2005 2006 2007 2008 2009 2010 2011 #توجيهي_2006 كمية من بخار الماء كتلتها (5) ودرجة حرارتها (130C) يُراد تبريدها وتحويلها إلى سائل بدرجة حرارة (50C) إذا علمت أن السعة الحرارية النوعية للبخار (2010J/kg.K)، والسعة الحرارية النوعية للماء 4200J/kg K ، والحرارة النوعية الكامنة لتصعيد الماء (10⁶×2.26 ، أحسب ما يأتي: أن كمية الطاقة المنطلقة (2) عند تبريد بخار الماء من (130) إلى ماء بدرجة حرارة (100) ب كمية الطاقة المنطلقة (2) عند تبريد الماء من (100) إلى ماء بدرجة حرارة (50) ج كمية الطاقة الكلية المنطلقة عند تبريد بخار الماء من (130) إلى ماء بدرجة حرارة (50). ... https://www.youtube.com/watch?v=v48MQNFDLKE

#أول_ثانوي #اول #توجيهي_2006 #جيل_2007 #منهاج_الأردن ... https://www.youtube.com/watch?v=IAVFYi5r4nc

CONDUCTORS 2.5.1 Basic Properties In an insulator, such as glass or rubber, each electron is on a short leash, attached to a particular atom. In a metallic conductor, by contrast, one or more electrons per atom are free to roam. (In liquid conductors such as salt water, it is ions that do the moving.) A perfect conductor would contain an unlimited supply of free charges. In real life there are no perfect conductors, but metals come pretty close, for most purposes. From this definition, the basic electrostatic properties of ideal conductors immediately follow: (1) E=0 inside a conductor. Why? Because if there were any field, those free charges would move, and it wouldn't be electrostatics any more. Hmm that's hardly a satisfactory explanation; maybe all it proves is that you can't have electrostatics when conductors are present. We had better examine what happens when you put a conductor into an external electric field E, (Fig. 2.42). Initially, the field will drive any free positive charges to the right, and negative ones to the left. (In practice, it's the negative charges-electrons that do the moving, but when they depart, the right side is left with a net positive charge the stationary nuclei-so it doesn't really matter which charges move; the effect is the same.) When they come to the edge of the material, the charges pile up: plus on the right side, minus on the left. Now, these induced charges produce a field of their own, Ej, which, as you can see from the figure, is in the opposite direction to Eo. That's the crucial point, for it means that the field of the induced charges tends to cancel the original field. Charge will continue to flow until this cancellation is complete. and the resultant field inside the conductor is precisely zero. The whole process is practically instantaneous (ii) p=0 inside a conductor. This follows from Gauss's law: V-Ep/60- If E is zero, so also is p. There is still charge around, but exactly as much plus as minus, so the net charge density in the interior is zero. (iii) Any net charge resides on the surface. That's the only place left. (iv) A conductor is an equipotential. For if a and b are any two points within (or at the surface of) a given conductor, V(b)V(a)-E-dl-0. and hence V(a) V(b). (v) E is perpendicular to the surface, just outside a conductor. Otherwise, as in (1), charge will immediately flow around the surface until it kills off the tangential component (Fig. 2.43) (Perpendicular to the surface, charge cannot flow, of course, since it is confined to the conducting object.)I think it is astonishing that the charge on a conductor flows to the surface. Because of their mutual repulsion, the charges naturally spread out as much as possible, but for all of them to go to the surface seems like a waste of the interior space. Surely we could do better, from the point of view of making each charge as far as possible from its neighbors, to sprinkle some of them throughout the volume... Well, it simply is not so. You do best to put all the charge on the surface, and this is true regardless of the size or shape of the conductor. 10 The problem can also be phrased in terms of energy. Like any other free dynamical system, the charge on a conductor will seek the configuration that minimizes its potential energy. What property (iii) asserts is that the electrostatic energy of a solid object (with specified shape and total charge) is a minimum when that charge is spread over the surface. For instance, the energy of a sphere is (1/8περ)(q2/R) if the charge is uniformly distributed over the surface, as we found in Ex. 2.9, but it is greater, (3/20περ)(q²/R), if the charge is uniformly distributed throughout the volume (Prob. 2.34). #electromagnetics #electrical #electrodynamics#potential 2.5.2 Induced Charges ... https://www.youtube.com/watch?v=P8XO-lBAB1Q

#أول_ثانوي #توجيهي_2006 #اول #منهاج_الأردن #جيل_2007 ... https://www.youtube.com/watch?v=Qmhk8zGUUSc