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Unformatted text preview: flows through a metal wire or other circuit elements, it encounters some resistance, depending on the properties of the material. The voltage (v) across an ideal resistor is proportional to the current (i) through it. The constant of proportionality is the resistance R. v iR Ohm’s law Ohm’s law is an empirical relationship. It is only an approximation and does not hold at very high voltage and current or at very low voltage and current. 16 EE1002 Introduction to Circuits and Systems i i 1 v R v Fig. Graphical representation of Ohm’s Law for resistance Resistance depends on the material as well as the geometry of the conductor: R l
A R l
A l A where is the resistivity of the material of the resistor; l , A are the length and cross‐sectional area of the resistor. Conductors have very low resistivity in the order of 10‐6 ohm‐meter ( m ) where as insulators have very high resistivity in the order of 1010 ohm‐meter ( m ) or more. Conductance 1
i 17 EE1002 Introduction to Circuits a...
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- Winter '14