Explanation:
(a) From E=
r
2
k
e
Q
Q=
k
e
Er
2
=
(8.99×10
9
N⋅m
2
/C
2
)
(8.90×10
2
N/C)(0.750m)
2
=5.57×10
−8
C
But Q is negative since
E
→
points inward, so
Q=−5.57×10
−8
C=−55.7nC
(b) The negatve charge has a spherically symmetric charge distribution, concentric with the spherical shell
