PASCO TD-8552 ELECTRICAL EQUIVALENT OF HEAT - Manual (Page 8)

Electrical Equivalent of Heat 012-02833D
4
Data
T
r
= _________________________________________
M
j
= _________________________________________
M
jw
= ________________________________________
V = _________________________________________
I = _________________________________________
t
i
= _________________________________________
t
f
= _________________________________________
T
i
= _________________________________________
T
f
= _________________________________________
Calculations
In order to determine the electrical equivalent of heat (J
e
), it is necessary to determine both
the total electrical energy that flowed into the lamp (E) and the total heat absorbed by the
water (H).
E, the electrical energy delivered to the lamp:
E = Electrical Energy into the Lamp = V
.
I
.
t = __________________________
t = t
f
- t
i
= the time during which power was applied to the lamp = ________
H, the heat transferred to the water (and the EEH Jar):
H = (M
w
+M
e
)(1 cal/gm C)(T
f
-T
i
) = __________________________________
M
w
= M
jw
- M
j
= Mass of water heated = ____________________________
M
e
= 23 grams. Some of the heat produced by the lamp is absorbed by the EEH Jar. For
accurate results, therefore, the heat capacity of the jar must be taken into acount (The heat
capacity of the EEH Jar is equivalent to that of approximately 23 grams of water.)
J
e
, the Electrical Equivalent of Heat:
J
e
= E/H = _______________________________________________________
Questions
➀ What effect are the following factors likely to have on the accuracy of your determination
of J
e
, the Electrical Equivalent of Heat? Can you estimate the magnitude of the effects?
a. The inked water is not completely opaque to visible light.
b. There is some transfer of thermal energy between the EEH Jar and the room atmosphere.
(What is the advantage of beginning the experiment below room temperature and ending
it an equal amount above room temperature?)
➁ How does J
e
compare with J, the mechanical equivalent of heat. Why?