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The energy stored in the electric field produced by a metal sphere is 4 . 5 J . If the sphere contains 4 μC charge, its radius will be: T a k e : 1 4 π ∈ 0 = 9 × 10 9 N m 2 C - 2

Options

  1. A32   mm
  2. B16   mm
  3. C28   mm
  4. D20   mm

Correct answer

B. 16   mm

Step-by-step solution

Energy of sphere = Q 2 2 C 4.5 = 16 × 10 - 12 2 C C = 16 × 10 - 12 9 = 4 π ε 0 R R = 16 × 10 - 12 9 × 1 4 π ε 0 R = 16 × 10 - 12 9 × 1 4 π ε 0 = 9 × 10 9 × 16 9 × 10 - 12 = 16 × 10 - 3 = 16   mm

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