Question

y=3.2

6. A resistor made out of Tungsten, (pw = 5.68 x 10-8 Nm andaw = 0.0045 ()-1 at 20 °C) has a cross section diameter of 0.7 mm and a Length of Y m. a) (3 points) What is the resistance of this wire at 20 °C. b) (3 points) What is the current I when this resistor is connected to a 120 V power supply? c) (6 points) What will be the current if the resistance temperature is increased by 1000 °C?

Answer 1

R= pe e- length teo ca) Resistance of a material is given by R=ge P= Resistivity " A= Area ao so -3.2m s=5.68X10-8 nm A Tid? , de diameter = 0.7mm = 0-7 X10-3m > A7 T (6-7X163) =) A= 0.385 X100 m2 R= (5.68X188) 3.2 0.385*10-6 | R= 6.472 07 4 . (6) By chm's law V=IR 120 • I-ě = 42 -I = 254.24 )

1 (1) Assuming Resistunity of Tungsten in a linear - function of Temperature P = So [1+4 (T-to) .: Srpe Scoi+ 4 (1006-20] Son = (5.48.-8) [i+ 0.6015 (580)] 1 = 30.73816-8 nm i. Reoso = 1 oso X e s Reoco i 30-73x108 x 3.2 - 0.3858186 2) Riooo = 2.550) - Rea nokatmshh P-R E24 лите/ better for tungsten in reality.