Question

A tungsten wire in a vacuum has length 16.0 cm and radius 6.00 mm. A potential difference is applied across it. (a) What is the resistance of the wire at 293 K? (b) Suppose the wire reaches an equilibrium temperature such that it emits 90.0 W in the form of radiation. Neglecting absorption of any radiation from its environment, what is the temperature of the wire? (Note: e = 0.320 for tungsten.) (c) What is the resistance of the wire at the temperature found in part (b)? Assume the temperature changes linearly over this temperature range. (d) What voltage drop is required across the wire? (e) Why are tungsten lightbulbs energetically inefficient as light sources? This answer has not been graded yot.

Answer 1

Answer iten - 16 m. wire And length Redius - 16.0cm 6.0 mm Resistirity of Tungslen at 2936 =5.6410-8 ohm And Alpha temperature coefficient of @ Tem Resistance = 0.004403 per degree Celsius. R = 5.6X10 $ x 0.16)/(x60.006)"} -7.93x102 e = o. 320 emit - gooow Stephan constant - 5.67X08 w mzury 96 -0.320 X 5.67 X10-8) XLC 257 X0-006x0.16) + 2018 6.006] T4 90 = 6887 to topy 1.1481010 T4. To = 1.1481010 T4 T4 = T= 7.89 x 104 942.6K ? 443K . = 670 Celsius

© Resistance at 670°C = {1+0.004403 *(943-293)} 87.93X105 ohm = 3.06410-4 or (ohm) voltage drop ris given below v2 3.06810 4 - go 22 90x3.06410-4 ~² = 0.0276 a balzu @ Tungsten light bulbs energetically in fficient as light sources because They emit more Heat than in