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5. The Potential of Electric Field
Electric field is potential, i.e. the work of its forces to transfer
electrical charge q between two points does not depend on the
trajectory form and is determined only by the initial and final positions

of charge. It is known that the work of forces for potential field is equal
to the decrease of potential energy:

A W W  q     (5.1)
1 2 1 2 1 2
where  - potential. Potential is a scalar quantity, which

characterizes the ability of a field to perform work and is determined
by the ratio of potential energy of test charge located at a given point of

the field, to value the charge

W
  (5.2)
q

Potential dimension:   J  V (joule per coulomb=volt).
C

Potential of point charge q at distance r is equal to
0

q
  (5.3)
4  r  
0

6. Equipotential surface

Geometric position of points having equal potential is called
equipotential surface. Fig. 6.1 shows them in dotted lines as
equipotential lines of point charge. The transferring charge along the

equipotential surface (  const , d  0) the work on the charge is not
performed.
It means that the field forces and strength lines are perpendicular to

equipotential surfaces.

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