Chapt. 25
Electric Potential
195
e) If a point charge of charge
q >
0 is put on the
x
axis exactly at
x
= 0, what is the net
force on it? What would happen to the point charge if it were slightly displaced along the
x
axis from
x
= 0? Assume that the point charge is constrained to move along the
x
axis:
for instance it may be thought of as a bead on a frictionless wire. Other than the force of
constraint assume that the only the Coulomb force due to the ring acts on the bead.
f) Assume the point charge from part (e) is displaced by a vanishingly small amount from
x
= 0 along the
x
axis and initially has zero velocity. The point charge has mass
m
. Derive
the point charge’s
VELOCITY
at
x
=
±∞
. Express the velocity in terms of
q
ring
,
q
,
b
,
and
m
?
025 qfull 00250 2 3 0 moderate math: 2 charges on a line
Extra keywords:
This needs fixing up in light of the similar question in ch.23.
3. Consider two charges
q
1
and
q
2
on the
x
axis at, respectively, points
x
1
and
x
2
:
x
2
>x
1
. The
zero of potential is at infinity.
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 Fall '06
 Buchler
 Physics, Charge, Electric Potential, Energy, Force, Potential Energy, Light, Electric charge, point charge

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