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*Question:* A particle of charge
is located
on the -axis at the point
. A second particle of
charge
is placed on the -axis at
. What is
the absolute electric potential at the origin ()? How much work must we perform in
order to slowly move a charge of
from infinity to the origin, whilst keeping
the other two charges fixed?

*Solution:* The absolute electric potential at the origin due to the first
charge is

Likewise, the absolute electric potential at the origin due to the second charge is

The net potential at the origin is simply the algebraic sum of the potentials due to each charge
taken in isolation. Thus,

The work which we must perform in order to slowly moving a charge from infinity to the origin is
simply the product of the charge and the potential difference between the end and beginning
points. Thus,

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** Previous:** Example 5.2: Motion of an
Richard Fitzpatrick
2007-07-14