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A chargedmetallic sphere A is suspended by a nylon thread another charged metallic sphere b heldby an insulating centers is 10 cmas shown in Fig. 1.7(a). The resulting repulsion of A is noted (for example, by shining a beam of light and measuring the deflection of its shadow on a screen). Spheres A and B are touched by uncharged spheres C and D respectively, as shown in Fig. 1.7(b). C and D are then removed and B is brought closer to A to a distance of 5.0 cm between their centers, as shown in Fig. 1.7(c). What is the expected repulsion of A on the basis of Coulomb’s law? Spheres A and C and spheres B and D have identical sizes. ignore the sizes ofa and b in comparison to the separation between theircenters |
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Answer» Solution :Letthe originalcharge on spere a be q and that on b beq at a distance r beteen THEIRCENTRES the magnitude of the `F=(1)/(4piepsilon_(0))(qq)/(r^(2))` NEGLECTING the sizes of sperhers aand b in comparionsto r when an identical but UNCHANGED spere c touches a the chargesredisitribute on a and c and by symmetry each sprere carries a charge `q//2`similary after d touchesb the rredistributedcharge on each isof the electrosatic FORCE on each is `F=(1)/(4pi epsilon_(0))((q//2)(q//2))/(r//2)^(2)=(1)/(4piepsilon_(0))(qq)/(r^(2))=F` THUS the electrostaticforce on a due to b remainsunaltered |
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