Physics 122 Circuits Test Name R V 1/Rp 1/R, + 1/R2 +1/R3 +.. Rs R1 R2 +R3 +....

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 tem

Explanation / 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

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