1) Determine the temperature at which the resistance of a tungsten wire will be

Question

1) Determine the temperature at which the resistance of a tungsten wire will be three times its value at 20°C. Assume its coefficient of resistivity remains constant.

2) A car owner forgets to turn off the headlights of his car while it is parked in his garage. If the 12.0-V battery in his car is rated at 89.0 A · h and each headlight requires 36.3 W of power, how long will it take the battery to completely discharge?

27 P058 Determine thve temperature at which the resistance of a tungaton wire will be rar response differs from the correct answer by more than 10%. Double check your calculabonsK three times its value at 20°C. Assume its coefficient of resistivity remains constant. Need Help? Pand I rated at 89.0 A h and each headlight requires 36.3 w of A car owner forgets to turn off the headlights of his car while it is parked in his garage. If the 12.0-V battery in hia carn er, how long will it take the battery to completely discharge? Need Help? O Type here to search 6 8 OP

Explanation / Answer

Rt=Rref(1+alpha(t-tref))

tref=20 oC

t=temperatue at resitance value halfed

Rref=R

Rt=R/2

R/2=R(1+alpha(t-20)

0.5=(1+alpha(t-20)

alpha(t-20)=-0.5

alpha=0.003819

0.003819(t-20)=-0.5

t-20=-130.92

t=130.92-20

t=-110.92 oC

I hope help you.....

2)

Since there are 2 headlights the total power is 72.6 W

Power is related to Voltage and current by:
P=IV

72.6=I*12

I=6.05A

1 A·h is one amp for one hour

So to find how many hours, we divide the rating by the amp usage:

89A.h/6.05A =14.71 h

I hope help you.....

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