Electric Currents and Circuits Summary (K. Honscheid Physics 112) CURRENT: Electric current is charge in motion. The amount of current is the charge per unit time that flows past some point. The direction of the current is conventionally taken as that of the flow of hypothetical positive charges, even though in most cases the current actually consists of negatively-charged electrons moving in the opposite direction. Current flows in the direction of the electric field in a conductor. I = Q / t OHM’S LAW: The current in a conductor is caused by a difference in electric potential along the direction of the current flow. Ohm’s law says that the current is directly proportional to the potential difference (voltage). V = R I Resistance: The resistance of an object depends on its geometry (length and cross-section area) and the material its made off (resistivity ) R = L / A POWER DISSIPATION: When a current flows in an ordinary conductor, electric energy is continually dissipated as heat. Microscopically, what happens is that the
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