Review17

# Review17 - Section 17.1: Electric Current The electric...

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Section 17.1: Electric Current The electric current I in a conductor is defined as t Q I Δ Δ [17.1a] where Δ Q is the charge that passes through a cross section of the conductor in time Δ t . The SI unit of current is the ampere (A); 1 A = 1 C/s. By convention, the direction of current is the direction of flow of positive charge. Section 17.2: A Microscopic View: Current and Drift Speed The drift speed is the average speed of charge carriers in a circuit. A typical drift speeds is a fraction of a millimeter per second. Section 17.4: Resistance, Resistivity, and Ohm's Law The resistance R of a conductor is defined as the ratio of the potential difference across the conductor to the current in it: I V R Δ [17.3] The SI units of resistance are volts per ampere, or ohms ( ); 1 = 1 V/A. If a conductor has length l and cross-sectional area A , its resistance is A R A ρ = [17.5] where ρ , is an intrinsic property of the conductor called the electrical resistivity . The SI unit of

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## This document was uploaded on 12/15/2011.

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Review17 - Section 17.1: Electric Current The electric...

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