2 minute read
Equipotential Lines
by AudioLearn
(although the sign will change because the potential energy is downhill). The electric field is therefore the gradient or slope of the electric potential, which will be downhill from an electrical standpoint.
One can define the electric potential of a point charge. In such cases, the electric potential of the point charge will be a constant multiplied by the charge and divided by the radius from the point charge. The constant is 9 x 109 Newton meters squared per coulomb squared. This means that the voltage decreases with distance, while the electrical field energy will decrease with the square of the distance. The voltage is considered to be taken as zero as the distance approaches infinity. The electric potential of a uniform sphere will be the same as what it would look like from a single point in the center of the sphere.
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EQUIPOTENTIAL LINES
Voltages can be described pictorially in the same way that electric fields were discussed in the previous chapter. As you can remember, the electric field lines radiate outward from a positive charge and end on negative charges. Equipotent lines can be described in two dimensions and equipotent surfaces can be described in three dimensions. These are places where the electric potential is constant. For a point charge, the equipotent lines are lines that connect potentials that are the same distance from the charge as is seen in figure 114:
Figure 114.
Equipotent lines are lines in which there is no work necessary to move the charge anywhere along the line. Work is necessary only to move a charge from one equipotent line to another. These lines will always be perpendicular to an electric field or to E. The potential will decrease as one spreads out from the central point. Any motion along an equipotent line must be perpendicular to the electric field.
The electric field of a conductor must be perpendicular to the conductor. This means that the conductor represents an equipotential surface as long as the situation is static. There is no voltage difference across the surface of a conductor. To fix the conductor voltage at zero volts, the conductor can be grounded to the earth in a process called “grounding”.
Figure 115 shows equipotent lines between positive and negative poles. These will look different, depending on whether the charges are negative and negative (and thus are repelling each other) or when the charges are positive and negative (and thus are attracting each other):
