Physics 122 Circuits Test Name R V 1/Rp 1/R, + 1/R2 +1/R3 +.. Rs R1 R2 +R3 +....
ID: 2038108 • Letter: P
Question
Physics 122 Circuits Test Name R V 1/Rp 1/R, + 1/R2 +1/R3 +.. Rs R1 R2 +R3 +.... 1) A household stove has a heating element that is made of tungsten wire. T coefficient of resistivity is ?-4.5 x 10-3 / °C and the supply voltage is 120 V. when stove is first turned ON the current is found to be 4.0 A and the initial temperatre of the s 38 °C. After heating for a short while the current is found to be reduced. Knowing th emperature of the wire depends upon the resistance calculate the temperature of the hen the current is 1.4 A he temExplanation / Answer
Initial Resistance at Ti=38oC
Ro=120/4 =30 ohms
Final Reistance at unknown temperature
R=120/1.4=85.714 ohms
Resistance Variation with temperature is given by
R=Ro[1+alpha*(T-To)]
85.714=30[1+(4.5*10-3)(T-38)]
T=450.7oC