- #1
Sullitp
- 2
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Hey so I am stuck on a 2part question, it goes as follows:
A tungstan filament in a light bulb is rated 75w for a 230v supply. The resistance of the filament at 20*C (*C means degrees celcius) is 68 ohm.
Assume a constant temperature coefficient of 0.005.
Calculate:
A) The hot resistance of the filament
Ok so I have no idea what temperature to use for "hot" so I used 100*C (I mean that's hot! )
Then used the equation R1=R0 (1+0.005x100) - Where
R1= Resistance at 100*C
R0= Resistance at 20*C
0.005= Temperature Coefficient
100= 100*C "Hot" temperature.
If you work this out it gives you a resistance of 102ohm @ 100*C.
I think that bit is right but is the 100*C right?
I have a second part to this so I'll put it in a different colour to help...
B) The operating temperature of the filament?
Well for this one I was going to use the formula (T1= R1/R0-1 All Divided By 0.005)
But turns out that gives you an operating temp of 100*C ... yea I am lost and have googled looking for operating temperature formulas...Help!
Thanks People!
A tungstan filament in a light bulb is rated 75w for a 230v supply. The resistance of the filament at 20*C (*C means degrees celcius) is 68 ohm.
Assume a constant temperature coefficient of 0.005.
Calculate:
A) The hot resistance of the filament
Ok so I have no idea what temperature to use for "hot" so I used 100*C (I mean that's hot! )
Then used the equation R1=R0 (1+0.005x100) - Where
R1= Resistance at 100*C
R0= Resistance at 20*C
0.005= Temperature Coefficient
100= 100*C "Hot" temperature.
If you work this out it gives you a resistance of 102ohm @ 100*C.
I think that bit is right but is the 100*C right?
I have a second part to this so I'll put it in a different colour to help...
B) The operating temperature of the filament?
Well for this one I was going to use the formula (T1= R1/R0-1 All Divided By 0.005)
But turns out that gives you an operating temp of 100*C ... yea I am lost and have googled looking for operating temperature formulas...Help!
Thanks People!