Homework chapter one:-H.W. 1.1: it is required to maintain a loading of 5 kW in a heating unit. At an initialtemperature of 15 C°, a voltage of 200 V is necessary for this purpose. When the unit issettled down to a steady temperature, a voltage of 220 V is required to maintain the sameloading. Estimate the final temperature of the heating element, if the resistancetemperature coefficient of the heating element is 0.0006 per C° at 0 Co.Answer: t2 = 368.15 C°H.W. 1.2: Determine the current flowing at the instant of switching a 60 watt lamp on a230 V supply. The ambient temperature is 25 C°. The filament temperature is 2000 C°and the resistance temperature coefficient is 0.005 /C° at 0 C°.Answer: I = 2.548 AH.W. 1.3: At 0 C°, a specimen of copper wire has its resistance equal to 4-milliohm andits temperature coefficient of resistance equal to (1/234.5) per Co. Find the values of itsresistance and temperature coefficient of resistance at 70 C°.Answer: Re= 5.194 m2, a70= 0.003284 / C°H.W. 1.4: At 0 C°, the resistances and their temperature coefficients of resistance of tworesistors 'A and 'B' are 80 ohm and 120 ohm, and 0.0038 per C° and 0.0018 per C,respectively. Find the temperature-coefficient of resistance at 0 C° of their seriescombination.Answer: a12 = 2.6 x 103 /C"H.W. 1.5: A D.C. shunt motor, after running several hours on constant voltage of 400 V,takes field current of 1.6 A. 1f temperature rise is 40 C°, what value of extra resistance isrequired in field circuit to maintain field current equal to 1.6 A. Assume motor startedfrom cold at 20 C° and a20 = 00043/Co.Answer: Rx 36.6894 21

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H.W. 1.1: it is required to maintain a loading of 5 kW in a heating unit. At an initial temperature of 15 C°, a voltage of 200 V is necessary for this purpose. When the unit is settled down to a steady temperature, a voltage of 220 V is required to maintain the same loading. Estimate the final temperature of the heating element, if the resistance temperature coefficient of the heating element is 0.0006 per C° at 0 C°.

H.W. 1.1: it is required to maintain a loading of 5 kW in a heating unit. At an initial temperature of 15 C°, a voltage of 200 V is necessary for this purpose. When the unit is settled down to a steady temperature, a voltage of 220 V is required to maintain the same loading. Estimate the final temperature of the heating element, if the resistance temperature coefficient of the heating element is 0.0006 per C° at 0 C°.

University Physics Volume 2

18th Edition

ISBN:9781938168161

Author:OpenStax

Publisher:OpenStax

Chapter9: Current And Resistance

Section: Chapter Questions

Problem 46P: An electronic device designed to operate at any temperature in the range from 10.0C to 55.0C...

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