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## Breakdown Voltage of a Sphere

What is the maximum charge that can be given to a sphere of diameter $$10cm$$ if the breakdown voltage of air is $$2\times10^4 V/cm$$? Discussion: Dielectric breakdown is when current flows through an electrical insulator when the voltage applied across it...

## Capacitance of a Spherical Capacitor

A spherical capacitor has inner radius $$a$$ and outer radius $$b$$. It is filled with an inhomogeneous dielectric with permittivity $$\epsilon=\epsilon_0K/r^2$$ for $$a<r<b$$. The outer sphere is grounded and a charge is placed on the inner sphere. Find the...