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cianfa72

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- About the Feynman discussion about charging a small metal ball from a charged hollow sphere

I keep reading the amusing lectures from Feynman on Electrodynamics. In particular in Lecture 5-8 figure 5-10, he argues that touching a charged hollow sphere

I was reasoning about the reason behind it. In section 19-1 Feynman uses the principle of minimum action to derive some interesting results. In this specific case the charge volume density vanishes (charges exist only as surface charge density on the conductors), so the principle claims that the target charge distribution when the small ball is in touch with the charged hollow sphere, corresponds to the surface charge distribution that produces a potential function that minimize the total electrostatic energy in all the space

I believe one can get the same result considering the matrix capacitance of the system of two conductors next to each other (i.e. the charged hollow sphere and the small metal ball). Then one may imagine that the two conductors are effectively "connected" through a non-capactive wire. This way the net result is setting up a Dirichlet problem where the capacitance matrix and the total charge are given/assigned.

What do you think about, does it make sense?

Thanks.

*externally*with a litte metal ball will cause the ball to pick up charge from the charged sphere (contrary touching the hollow sphere from the inside will not cause any charge to be pushed on the small ball since the electric field inside the hollow sphere vanishes).I was reasoning about the reason behind it. In section 19-1 Feynman uses the principle of minimum action to derive some interesting results. In this specific case the charge volume density vanishes (charges exist only as surface charge density on the conductors), so the principle claims that the target charge distribution when the small ball is in touch with the charged hollow sphere, corresponds to the surface charge distribution that produces a potential function that minimize the total electrostatic energy in all the space

*surrounding*the two conductors.I believe one can get the same result considering the matrix capacitance of the system of two conductors next to each other (i.e. the charged hollow sphere and the small metal ball). Then one may imagine that the two conductors are effectively "connected" through a non-capactive wire. This way the net result is setting up a Dirichlet problem where the capacitance matrix and the total charge are given/assigned.

What do you think about, does it make sense?

Thanks.

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