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Power Dissipated in a Resistor

# Power Dissipated in a Resistor - Physics 202 Tuesday March...

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Physics 202 Tuesday, March 2, 1999 Announcements: Midterm 2 scheduled for March 18, 1999 Lecture notes: Temperature dependence of ρ R= ρ L/A For metals: ρ =ρ o [ 1+ α( T- T o )], α 0 For Semiconductors such as germanium and silica: Power Dissipated in a Resistor

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b to c and d to a the circuit is ideal: There is no resistance c to d is a resistor Let's follow a quantity of positive charge Q that flows around the circuit. As Q moves from a to b (through the battery), its electrical potential energy increases by an amount [V Q ] o The chemical potential energy in the battery decreases by the same amount. As Q moves from c to d, through the resistor, the charge carried suffers "collisions" with the (misplaced) atoms in the the resistor and loses energy, by the same amount [V Q ] o The energy is disipated as heat or thermal energy By the time Q reaches point a, it is at the same electric potential again. o U/ t = ( Q / t) V = IV = P o P is the power lost in the resistor; conversely the power supplied by the battery Let's check the units for P...
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