18. We use Eq. 23-3, assuming both charges are positive.
E
left ring
=
E
right ring
evaluated at
P
q
1
R
4πε
0
(R
2
+ R
2
)
3/2
=
q
2
(2R)
4πε
0
((2R)
2
+ R
2
)
3/2
Simplifying, we obtain
q
1
q
2
= 2
2
5
3/2
≈ 0.51 .
18. We use Eq. 23-3, assuming both charges are positive.
E
left ring
=
E
right ring
evaluated at
P
q
1
R
4πε
0
(R
2
+ R
2
)
3/2
=
q
2
(2R)
4πε
0
((2R)
2
+ R
2
)
3/2
Simplifying, we obtain
q
1
q
2
= 2
2
5
3/2
≈ 0.51 .