Question

Course Contents >> ... >> Problemas III >> 20.38 - Resistance and Resistivity Timer Notes Evaluate Feedback Print A tungsten filament has a resistance of 0.370 at room temperature (20.0°C). What is the resistance of the filament when the temperature is increased to a typical operating temperature of 2820°C when the thermal expansion of the tungsten filament is taken into account? The thermal expansion coefficient of tungsten is 1.20x10-5/°C. 0.3824ohm Submit Answer Incorrect. Tries 1/3 Previous Tries By what percentage does your answer differ if thermal expansion is neglected? Enter as a negative percent if the resistance with thermal expansion taken into account is less than when the expansion is neglected. (You do not need to enter any units.) 3.35 Submit Answer Incorrect. Tries 1/3 Previous Tries This discussion is closed. Send Feedback

Answer 1

(T) = 20c Solution - For A tungsten filament Resistance (Ro) = 0.370 52 At Temprature Thermal expansion coofficient of tungsten (X) = 1-20 x15% Temprature increases to (T) = 2820° Resistance becomes (R) - Ro(1+2 OT) R- (0.370) (1 + 1.20x%-$(2820 - 20) R = 0.370 (1+0.0336) 0.38252 IR At T = 28200 = 0.38252 If expansion neglected; Resistance is (R) = 0.37052 Percentange R- Ro change 0-382-0. 370 x 100 xloo Ro 0.370 3.24%