InterviewSolution
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InterviewSolution
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Show that the force on each plate of a parallel plate capacitor has a magnitude equal to (1)/(2)QE, where Q is the charge on the capacitor and E is the magnitude of electric field between the plates. Explain the origin of the factor (1)/(2). |
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Answer» Solution :Let the application of force F increases the distance between the plates by `trianglex`. Work done by the external force `=F*triangle x` This increases the energy. Energy DENSITY = u So, INCREASE in energy `= u(alpha triangle x) ""[alpha = " area of the plate "]` `:. F* trianglex = u alpha "" triangle x " or, " F = u alpha` `:. F = (1)/(2)in_0 E^2* alpha ""[:. u = (1)/(2) in_0E^2]` `:. F = (1)/(2) in_0 alpha E*E = (1)/(2) QE` The factor `(1)/(2)` arises in this relation due to the fact that average `(E )/(2) " of "0` and E is taken. |
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