Chapter 23 Electric Potential

• Electric potential energy (sec. 23.1)• Electric potential (sec. 23.2)• Calculating elec. potential (sec. 23.3)• Equipotential surfaces(sec. 23.4)• Potential gradient (sec. 23.5)

C 2012 J. Becker

Learning Goals - we will learn: ch 23

• How to calculate the electric potential energy (U) of a collection of charges.

• The definition and significance of electric potential (V).

• How to use the electric potential to calculate the electric field (E).

POSITIVE charge moving in an E field.

(a) When a positive charge moves in the direction of an electric field, the field does positive work

and the potential energy decreases. Work = qo

E d

The charge qo moves along a straight line extending radially from charge q.

The work done on charge qo by the electric field produced by charge q depends only on the distances ra and rb.

Graphs of the potential energy U of two point charges q and q0 versus their

separation r.

The potential energy associated with a charge qo at point “a” depends on charges q1, q2, and q3 and on their distances r1, r2,

and r3 from point “a.”

Calculating the electric potential by integrating E.dl for a single point charge.

In both cases (positive or

negative point charges), if you move qo in the

direction of F, the electric potential V

decreases; if you move qo in

the direction opposite F, V

increases.

+qo Test charge

Electric field E and potential V at points inside and outside a

positively charged spherical

conductor.

E = dV / dr

All charges in the ring (Q) are the same distance a from point P on the ring axis.

Find the potential V at point P on the axis of the

ring.

Find the potential V at

point P.

Find the electric potential on the perpendicular bisector of a charged rod.

See www.physics.sjsu.edu/becker/physics51

Review

C 2012 J. F. Becker