Saturday, July 26, 2014

electrostatics - Is potential difference or potential used in defining capacitance?


In my textbook I came across the capacitance of a certain body (i.e. a sphere, not two different spheres as in a spherical capacitor) and in it the formula,



$$Q = CV$$


where $V$ is the potential of the body with respect to the Earth. Now in a parallel plate capacitor, why do we choose the potential difference and not the potential of a single plate to the Earth?



Answer



V in th either situation is potential difference but in the case of an isolated sphere as written in Halliday/Resnick ( Indian edition)



We can assign a capacitance to a single isolated spherical conductor of radius R by Assuming that the " missing plate " is a conducting sphere of infinite radius



So the potential on single sphere comes out to be potential difference


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