Electrostatic Potential Energy
When the forces between a system of particles are conservative, a potential energy function can be assigned to the system. When the system changes its configuration, the conservative force does some work and there is a change in potential energy of the system.
The charge in potential energy is defined as negative of work done by conservative force (or electric force) during the charge.
Uf - Ui = -Wcons = -We
If reference level of potential energy (datum) is taken, when the separation between the particles is infinite, then for a particular configuration having potential energy U,
is the work done by conservative force during the arrangement
U - 0 = -
U = -
For examples:
When the forces between a system of particles are conservative, a potential energy function can be assigned to the system. When the system changes its configuration, the conservative force does some work and there is a change in potential energy of the system.
The charge in potential energy is defined as negative of work done by conservative force (or electric force) during the charge.
If reference level of potential energy (datum) is taken, when the separation between the particles is infinite, then for a particular configuration having potential energy U,
For examples:
- A proton is fixed and an electron is moved from
to a point near the proton,
> 0 (
force and displacement are in same direction). This means
U < 0, i.e. potential energy decreases.
- A proton is fixed and another proton is moved from
to a point near it,
< 0
U > 0
- In figure (1), potential energy decreases as WE > 0.
In figure (2), potential energy increases as WE < 0.
In figure (3), potential energy decreases as WE > 0.
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