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Problem 26.12: Calculate capacitance of concentric spheres

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The animation shows a spherical conductor surrounded by a conducting spherical shell. The two conductors have equal but opposite charge and the voltage difference between the two is 50 V (position is given in centimeters and charge is given in nanocoulombs). The field vectors for the electric field (kQ/r2) are shown in the region between the shell and the inner sphere and are zero everywhere else. Restart.

  1. Develop an expression for the charge as a function of the radius of the outer sphere and verify it with the animation.
  2. Develop an expression for the capacitance as a function of radius.
  3. Does the capacitance increase or decrease with increasing shell size? Explain.

Problem authored by Anne J. Cox.

Physlets were developed at Davidson College and converted from Java to JavaScript using the SwingJS system developed at St. Olaf College.

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