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Set up for the class a model of an electric circuit, using wires, bulbs, and a battery. Demonstrate the properties of insulation and conductivity by testing several different materials.
Insulated Wires: The NEC-2 Way. n episode #50 of this series, I called attention to the IS (Insulated Sheath) card introduced into NEC-4. The program control command provides a means to factor into a model the effects of the conductivity and permittivity of insulation wrapped around a wire.
Explain what an insulator is. List the differences and similarities between conductors and insulators. Describe the process of charging by induction. In the preceding section, we said that scientists were able to create electric charge only on nonmetallic materials and never on metals.
We define a conductor as a material in which charges are free to move over macroscopic distances—i.e., they can leave their nuclei and move around the material. An insulator is anything else. In an insulator the charge distribution in an atom may change, but the charges do not leave their nuclei.
The following chart is a guideline of “ampacity”, or copper wire current-carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated “ampacities” are just a rule of thumb. In careful engineering the insulation
Lecture begins with a recap of Gauss’s Law, its derivation, its limitation and its applications in deriving the electric field of several symmetric geometries—like the infinitely long wire. The electrical properties of conductors and insulators are discussed.
Let’s consider an insulated conductor. Earlier we have studied that whenever we place an excess amount of charge inside of a conducting medium, it immediately moves to the surface due to the Coulomb repulsive force and we end up with no net charge enclosed inside of the conducting medium.
