*18.  A tungsten wire has a radius of 0.075 mm and is heated from 20.0 to 1320 °C. The temperature coefficient of resistivity is a = 4.5 x 10-3 (C°)-1. When 120 V is applied across the ends of the hot wire, a current of 1.5 A is produced. How long is the wire? Neglect any effects due to thermal expansion of the wire.

 

Ohm’s law gives us

 

Solve for L

 

 

 

 

 

 

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This page last updated on June 14, 2018