The electric field and the electric potential are intimately connected. In fact, they are simply two different perspectives on how source charges alter the space around them.

• The electric potential can be found if you know the electric field.

• The electric field can be found if you know the electric potential.

• Electric field lines are always perpendicular to equipotential surfaces.

• The electric field points “downhill” in the direction of decreasing potential.

• The electric field is stronger where equipotentials are closer together.

《 LOOKING BACK Sections 25.4, 25.5, and 25.6 The electric potential and its graphical representations

You’ll learn about the properties of conductors in electrostatic equilibrium, finding the same results as using Gauss’s law:

• Any excess charge is on the surface.

• The interior electric field is zero.

• The exterior electric field is perpendicular to the surface.

• The entire conductor is an equipotential.

A potential difference—voltage—is created by separating positive and negative charges.

• Work must be done to separate charges. The work done per charge is called the emf of a device. Emf is measured in volts.

• We’ll use a charge escalator model of a battery in which chemical reactions “lift” charges from one terminal to the other.

  

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Any two electrodes with equal and opposite charges form a capacitor. Their capacitance indicates their capacity for storing charge. The energy stored in a capacitor will lead us to recognize that electric energy is stored in the electric field.

《 LOOKING BACK Section 23.5 Parallel-plate capacitors

Capacitors are important circuit elements that store charge and energy.

• You’ll learn to work with combinations of capacitors arranged in series and parallel.

• You’ll learn that an insulator—called a dielectric—between the capacitor plates alters the capacitor in useful ways.