Current and Resistance
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Textbook
University Physics Volume 2: Chapter 9
Current and Resistance
Theory
Current and Current Density
Electric current () is the flow of electric charge through a conductor, measured in amperes (). The current density () represents the current per unit cross-sectional area, expressed as: where is the conductivity, and is the electric field.
Resistance, Resistivity, and Conductivity
Resistance () quantifies the opposition to the flow of current in a conductor, measured in ohms (). Resistivity () is a material property that measures resistance per unit length and cross-sectional area. Conductivity () is the inverse of resistivity.
where is the length of the conductor and is its cross-sectional area.
Ohm's Law
Ohm's Law relates the voltage (), current (), and resistance () in a circuit:
It also applies at the microscopic level:
Ohm's Law Simulation
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