Question

3.5 Temperature sensing in a light bulb. Incandescent light bulbs use a tungsten wire as the light-radiating filament by heating it to a temperature at which it is bright enough to produce light. The temperature of the wire can be estimated directly from the power rating and the resistance of the wire when it is cold. Given a 120 V, 100 W light bulb with a resistance of 22 W at room temperature (20 C): (a) Calculate the temperature of the filament when the light bulb is lit. (b) What are the possible sources of error in this type of indirect sensing

Answer 1

Following are the solution to the given points:

Step-by-step explanation:

In point a:

Given:

`Temperature =20^(\circ ) \ C, \\\\Resistance (R_o) = 22 \Omega`

However, the resistance of the bulb is 120 V or 100 W.

`R= (v^2)/(P)=(120^2)/(100) =144 \Omega`

Let Tungsten's standard temperature coefficient be = 0.0045
`20^(\circ) \ C`

Calculating temperature:

`\to R=R_0(1+ \alpha (T-T_0))`

`\to 144=22(1+0.0045(T-20))\\\\\to 144=22+0099(T-20)\\\\\to T -20 1232.32\\\\\to T =1252.32^(\circ ) \ C \\`

In point b:

Potential consequences for indirect failures on iridescent bulb power device atmosphere does have a minor impact on defects, humidity, pressure, and surface that light bulb within the glass as well as the sensor attributable to the mercury.