TABLE OF CONTENTS by Glen Ballou
Resistance 1-3 is associated with the phenomenon of energy dissipation. In its simplest form, it is a measure of the opposition to the flow of current by a piece of electric material. Resistance dissipates energy in the form of heat; the best conductors have low resistance and produce little heat, whereas the poorest conductors have high resistance and produce the most heat. For instance, if a current of 10 A flowed through a resistance of 1 ?, the heat would be 100 W. If the same current flowed through 100 ?, the heat would be 10,000 W, which is determined by the equation
| (10-1) |  |
where,
P is the power in watts,
I is the current in amperes,
R is the resistance in ohms.
In a pure resistance, the voltage and current relationship remains the same; therefore, the voltage drop across the resistor is
| (10-2) |  |
where,
V is the voltage in volts,
I is the current in amperes,
R is the resistance in ohms.
Resistors are fixed or variable and can have tolerances from 0.5% to 20% and power ranges from 0.1W to hundreds of watts
Resistors will change value as a result of applied voltage, power,...
