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- Resistance of a Conductor
- Resistance R of a conductor is defined by
- Similarly the resistivity and conductivity of a material is defined by
- Resistance of a conducting wire of length L and uniform cross section is
- PHY102 Physics II © Dr.Cem Özdoğan
- Current
- The electric current i in a conductor is defined by
- Current Density
- Current is related to current density by
- Change of ρ with Temperature
- The resistivity of most material changes with temperature and is given as
- Drift Speed of the Charge Carriers
- Drift speed of the charge carriers in an applied electric field is related to current density by
- Ohm’s Law
- A given device (conductor, resistor, or any other electrical device) obeys Ohm’s law if its resistance R (defined by Eq. 26-8 as V/i) is independent of the applied potential difference V.
- Resistivity of a Metal
- By assuming that the conduction electrons in a metal are free to move like the molecules of a gas, it is possible to derive an expression for the resistivity of a metal:
- Power
- The power P, or rate of energy transfer, in an electrical device across which a potential difference V is maintained is
- If the device is a resistor, we can write