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Question

Show your work clearly for credit. Be and box your answers to the problems. At 60.0 degree C, a certain material has a resistance that is twice as large as its resistance at 20.0 degree C. 1.1. What Is the thermal coefficient of resistivity for this material? A resistor made of this material has a length of 2.00 cm and a radius of 5.00 mm. If its resistance is 80.0 k Ohm, what is the resistivity for this resistor? The resistor is placed in a circuit such that 6.00 mA of current flow through it. If the resistor has an electron density of 2.39 times 1023 electrons/m3, what is the drift speed of the electrons? What is the potential difference across the resistor while in this circuit?

Explanation / Answer

1. let te thermal coefficient be x.
then R*(1+x*(60-20))=2*R

1+40*x=2

x=1/40=0.025 / degree celcius

2.length=2 cm=0.02 m
radius=5 mm=0.005 m
area=pi*radius^2=7.854*10^(-5) m^2

as we know resistance=resistivity*length/area

80*1000=resistivity*0.02/(7.854*10^(-5))

resistivity=314.16 ohms.m

3.

we know that

drift speed=current/(charge density*cross sectional area*unit charge)

=0.006/(2.39*10^23*pi*0.005^2*1.6*10^(-19))=1.9978 mm/sec

approximately 2 mm/sec

4.. as current is 6 mA and ressitance is 80 kilo ohms,

voltage difference=80*1000*0.006=480 volts

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