The Battery Revisited

Earlier in this chapter, during the introduction of voltage, I mentioned that a neutral conductor like a wire or metal plate that is brought close to a battery will not be affected by the battery. Even if the battery or

Figure 2.15 Electric field of DC voltage across a conducting wire. Arrowheads show the direction of the electric field. Voltage is shown by shade inside the conductor and as contours outside the conductor. This figure was created using Ansoft Corporation's Maxwell 2D field solver software (http://www.ansoft.com).

Figure 2.15 Electric field of DC voltage across a conducting wire. Arrowheads show the direction of the electric field. Voltage is shown by shade inside the conductor and as contours outside the conductor. This figure was created using Ansoft Corporation's Maxwell 2D field solver software (http://www.ansoft.com).

capacitor has a very high voltage, you will not see a spark (static discharge) develop to a third conductor. Why not?

To avoid discussing the details of the electrochemistry inside a battery, let's assume that we have a capacitor charged to a large voltage. One plate has many positive charges and the other plate has many negative charges. The net charge of the capacitor is neutral. Now bring a neutral, isolated metal ball near to the negative terminal. A slight charge is induced in the wire, but not much because most of the negative charge has a greater attraction to the other plate of the capacitor. Furthermore, we will not see a spark because the capacitor as a whole has a neutral charge. Suppose that charge did start to leave the capacitor to jump to the neural sphere. The capacitor would then have a charge imbalance and the charge would be attracted right back.

Table 2.1 Low-Frequency (DC) Conductivity and Permittivity of Various Materials

Conductivity,

Material

1/[Wm]

Permittivity (Dielectric Constant x e0)

Copper

5.7 x 107

1 x eo

Stainless steel

106

1 x eo

Salt water

~4

80 x e0

Fresh water

~10-2

80 x e0

Distilled water

~10-4

80 x e0

Animal muscle

0.35

[no data]

Animal fat

4 x 10-2

[no data]

Typical ground (soil)

~10-2 to 10-4

3 xe0 to 14 x e0

Glass

~10-12

~5 x e0

Table 2.1 data adapted from Krauss and Fleisch, Electromagnetics with Applications, 5th Edition, Boston: McGraw-Hill, 1999, and from Paul and Nasar, Introduction to Electromagnetic Fields, 2nd Edition, New York: McGraw-Hill, 1987.

Table 2.1 data adapted from Krauss and Fleisch, Electromagnetics with Applications, 5th Edition, Boston: McGraw-Hill, 1999, and from Paul and Nasar, Introduction to Electromagnetic Fields, 2nd Edition, New York: McGraw-Hill, 1987.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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