PASCO TD-8552 ELECTRICAL EQUIVALENT OF HEAT - Manual (Page 9)

012-02833D Electrical Equivalent of Heat
5
Experiment 2: Efficiency of an Incandescent Lamp
Repeat Experiment 1, except do not use the India ink (step 4) or the styrofoam Calorimeter
(step 7). Record the same data as in Experiment 1, and use the same calculations to deter-
mine E and H. (Convert H to Joules by multiplying by J
e
from the first lab.)
In performing the experiment with clear water and no Calorimeter, energy in the form of
visible light is allowed to escape the system. However, water is a good absorber of infrared
radiation, so most of the energy that is not emitted as visible light will contribute to H, the
thermal energy absorbed by the water.
The efficiency of the lamp is defined as the energy converted to visible light divided by the
total electrical energy that goes into the lamp. By making the assumption that all the energy
that doesn't contribute to H is released as visible light, the equation for the efficiency of the
lamp becomes:
Efficiency = (E - H
j
)/E.
Data
T
r
= ________________________________________
M
j
= ________________________________________
M
jw
= ________________________________________
V = ________________________________________
I = ________________________________________
t
i
= ________________________________________
t
f
= ________________________________________
T
i
= ________________________________________
T
f
= ________________________________________