GEN PHYS 2 | Electric Potential (WW2 Reviewer)

What happens to the work done and potential energy of a positive test charge when it moves towards a negatively charged area?

The work done by the electric field is positive, meaning the potential energy decreases.

What happens to the work done and potential energy of a positive test charge when it moves towards a positively charged area?

The work done by the electric field is negative, meaning the potential energy increases.

Electric Potential Energy

• work done by the electric field to bring the charge from a source point to a reference point (usually one of more infinite distance)

• only depends on the endpoints

• is scalar, can be positive or negative

• value approaches zero as the displacement/distance increases

What is the relationship between electric potential energy and displacement when the test charge and the source charge have the same sign?

As the displacement increases, the potential energy decreases.

What is the relationship between electric potential energy and displacement when the test charge and the source charge have different signs?

As the displacement increases, the potential energy increases.

Electric Potential Energy of Several Charges

Following the superposition principle, the total work done on a test charge during any displacement is the sum of the contribution from the individual charges.

Electric Potential

• amount of electric potential energy per unit charge at a specific point in the field

• how much work is needed to move a test charge without any acceleration from a reference point (usually from infinity) to a specific point in the field

• has the SI unit Joules/Coulomb

Electric Potential Difference

difference of electric potential between two points

Electric Potential in a Positive Test Charge’s Electric Field

• V increases as you move inward

• V decreases as you move outward

Electric Potential in a Negative Test Charge’s Electric Field

• V decreases as you move inward

• V increases as you move outward

Equipotential Surface

3D surface where electric potential is the same at every point

Characteristics of Equipotential Surfaces

• Field lines and equipotential surface are always mutually perpendicular

• no need to move charged particles along equipotential lines

Electric Field and Electric Potential

The electric field is the negative derivative of electric potential.