The energy stored in the electric field produced by a metal sphere is 4.5 J. If the sphere contains 4 $\mu $C charge, its radius will be : [ Take : ${1 \over {4\,\pi { \in _0}}} = $ 9 $ \times $ 109 N $-$ m2/C2 ]

Question

The energy stored in the electric field produced by a metal sphere is 4.5 J. If the sphere contains 4 $\mu $C charge, its radius will be :
[ Take : ${1 \over {4\,\pi { \in _0}}} = $ 9 $ \times $ 10⁹ N $-$ m²/C² ]

20 mm