Educator

Electric Current

• The current is the rate of flow of charge. If you take a cross-section of a wire and count how many Coulombs flow the cross-section in one second, the will be the current, expressed in C/s, or A (Ampere).
• In a wire with uniform cross-sectional area A, the current can be shown to be equal to Anqv where n is the number of charge carriers (in conductors, these are electrons), q is the charge carried by a charge carrier, and v is the drift velocity of the charge carriers.
• Ohm’s law: V = I R. The potential difference across a wire is equal to the resistance R of the wire, times the current in the wire.
• For a wire of uniform cross-sectional area A and length L, the resistance is given by R = (rho) L / A, where rho is the resistivity of the material from which the wire is made.