What is the capacitance of a spherical capacitor formed by two concentric conducting spheres of radii and () with vacuum between them, when the outer sphere is grounded?
Answer and explanation
Correct answer: B.
- Step 1: For a charge on the inner sphere of radius and on the outer grounded sphere of radius , the electric field between them () is .
- Step 2: The potential difference between the spheres is .
- Step 3: Capacitance is .
Answer
.
Why not the others: adds the radii in denominator; has incorrect dimensions; has cylindrical prefactor.
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