Electrical Potential EnergyChapter 18.1

Electrical Potential Energy• Electrical Potential Energy – Potential energy associated with

an object due to its position relative to a source of electric force.

• Similar to how the gravitational force associated with an object's position relative to earth creates gravitational potential energy.

Work in an Electric Field• A charged object can have potential energy by virtue of its

location in an electric field.

• Work is required to push a charged particle against the electric field of a charged body.

Uniform Electric Field• The electrical potential energy can be associated with a charge

in a uniform field.• The electric potential energy will increase if the charge is

negative and decrease if the charge is positive.

Electric Potential Energy in a Uniform Electric Field

• This equation is only valid in a uniform electric field• Field lines are equally spaced apart in the entire electric field.

Electric Potential Pair of Charges• Electrical potential energy can be associated with a pair of

charges.• Because the electric field is no longer uniform, a new equation

must be used to describe the electric potential energy.

Electrical Potential Energy for a Pair of Charges

• Positive work must be done to bring the charges together, so the electrical potential energy is positive for like charges and negative for unlike charges.

• The expression can be used to determine the electrical potential energy for two or more charges.

Example Problem• In the classical model, an electron has a radius of

r = 2.82x10-15m. Thus, two electrons could be as close as 2r. Calculate the electrical potential energy for two electrons that are touching.

Example Answer