5
Fundamentals of Electric Capacitors
Equation (1.6) indicates that the longer the distance from the charge, the smaller
the electric potential, and the shorter the distance toward the charge, the larger
the electric potential. In extreme cases, r becomes infinite and the electric voltage
becomes zero; if the distance becomes zero, the electric potential will become
infinite regardless of how large or small the charge magnitude is.
1.2.3 Implication of Electric Potential in Capacitor Cell Voltage
Figure 1.3 displays a capacitor with positive charge of Q + uniformly distributed on a positive planar electrode and negative charge of Q on the negative
–
electrode. Here |Q + | = |Q |. The planar surface is A and the vacuum space
–
between the two planar electrodes has a dielectric constant of ε 0 and a distance of d [2]. According to Gauss’ law, the electric field outside of the planar
conductive surface can be expressed as
Q
E =
+
A
(1.7)
ε 0
The potential difference between the electrodes can be treated as the work
done to move the charge from the positive electrode to the negative electrode. Similar to Equation (1.5), the work or electric difference between two
electrodes (ΔV) can be expressed as
Plate Separation Distance
d
Charge Q +
Charge Q
–
Electric field E
Plate area A
Dielectric ε
FIGURE 1.3
(See color insert.) Charged capacitor device.
Fundamentals of Electric Capacitors
Equation (1.6) indicates that the longer the distance from the charge, the smaller
the electric potential, and the shorter the distance toward the charge, the larger
the electric potential. In extreme cases, r becomes infinite and the electric voltage
becomes zero; if the distance becomes zero, the electric potential will become
infinite regardless of how large or small the charge magnitude is.
1.2.3 Implication of Electric Potential in Capacitor Cell Voltage
Figure 1.3 displays a capacitor with positive charge of Q + uniformly distributed on a positive planar electrode and negative charge of Q on the negative
–
electrode. Here |Q + | = |Q |. The planar surface is A and the vacuum space
–
between the two planar electrodes has a dielectric constant of ε 0 and a distance of d [2]. According to Gauss’ law, the electric field outside of the planar
conductive surface can be expressed as
Q
E =
+
A
(1.7)
ε 0
The potential difference between the electrodes can be treated as the work
done to move the charge from the positive electrode to the negative electrode. Similar to Equation (1.5), the work or electric difference between two
electrodes (ΔV) can be expressed as
Plate Separation Distance
d
Charge Q +
Charge Q
–
Electric field E
Plate area A
Dielectric ε
FIGURE 1.3
(See color insert.) Charged capacitor device.