3B SCIENTIFIC PHYSICS 1008523 Manual de instrucciones - Página 3
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Imprimir página5.2 Measurement of radiant intensity as a
function of the temperature of the fila-
ment
Connect the thermopile to the P3340 digital
multimeter (1002785).
Set up the Stefan-Boltzmann lamp in front
of the thermopile and connect up the DC
power supply and the two P1035 digital mul-
timeters (1002781).
Apply a voltage in steps of 1 V up to a max-
imum of 12 V, measure the lamp voltage U,
the lamp current I, and use the thermopile
to measure the radiant intensity (5.3,
Tab. 2).
5.3 Evaluation
Calculate R = U/I (Tab. 2).
Now the values determined, T
be used along with the temperature coeffi-
cient
of
resistance
= 4.4 · 10
K
to calculate the tempera-
-3
-1
ture of the filament by means of the follow-
ing formula (Tab. 2):
R
R
ref
T
T
R
ref
, R
, R, can
ref
ref
for
tungsten
.
ref
One possible alternative method for determin-
ing the temperature T of the filament is to calcu-
late the quotients R/R
Tab. 3 to find the temperature.
Note: In Table 3 the quotient R/R
for T
= 300 K and for T
ref
to determine the temperature more precisely by
interpolating between these two reference val-
ues to take account of the actual room temper-
ature.
Plot as a function of T
Tab. 2: Values for the resistance R and the tempera-
ture T of the filament calculated from the
measured values for the lamp voltage U and
the lamp current I, as well as the radiated in-
tensity measured with the thermopile
U / V
I / A
0.00369
0.006
1.0502
0.554
2.033
0.706
3.012
0.837
4.003
0.958
5.012
1.071
6.017
1.174
7.074
1.276
8.028
1.362
9.011
1.446
10.088
1.534
11.02
1.607
11.685
1.68
3
and then use Fig. 2 or
ref
is specified
ref
= 290 K. It is possible
ref
(Fig. 3).
4
/ V
R / Ω
T / K
0.615
328
0
1.896
854
0.0001
2.879
1259
0.0004
3.599
1554
0.0011
4.178
1792
0.0019
4.679
1998
0.0029
5.125
2181
0.0042
5.5434
2353
0.0058
5.894
2497
0.0072
6.232
2636
0.0088
6.576
2777
0.0106
6.8575
2893
0.0125
6.955
2933
0.0145