1. The document describes an experiment conducted to determine the mechanical equivalent of heat (J) using an electrical method. A calorimeter containing water was heated by an electric current passing through a coil submerged in the water. 2. The temperature increase of the water was measured over time as it absorbed the heat from the current. Calculations using the temperature change, mass of the calorimeter components, and their specific heats allowed determining the heat absorbed. 3. Dividing the electrical energy input by the heat absorbed gave the value of J as 5.15 J/cal. The experiment was successful in obtaining a value for J close to expectations. Radiation corrections were also applied to temperature readings.

1. AMERICAN INTERNATIONAL UNIVERSITY–BANGLADESH (AIUB)
FACULTY OF SCIENCE & TECHNOLOGY
DEPARTMENT OF PHYSICS
PHYSICS 2 LAB
Summer 2021-2022
Section: ______, Group: 06
LAB REPORT ON
Title of the Report
TO DETERMINE THE VALUE OF J, THE MECHANICAL EQUIVALENT OF HEAT BY
ELECTRICAL METHOD.
Supervised By
Dr. Shovan Kumar Kundu
Submitted By
Name ID Contribution Signature
1.
2.
3.
4.
5.
6.
Date of Submission: month d

2. TABLE OF CONTENTS
TOPICS Page no.
I. Title Page 1
II. Table of Content 2
1. Theory 3
2. Apparatus 3
3. Procedure 4
4. Experimental Data 5
5. Analysis and Calculation 7
6. Result 8
7. Discussion 8
8. References 8
Lab Report Department of Physics Page 3 of

3. 1.Theory: The mechanical equivalent of heat J is the number of Joules of electrical
energy required to generate one calorie of heat.
If V volt be the potential difference across a conducting coil and 𝑖 ampere be the
current flowing through the coil in 𝑡 seconds, then electrical energy expended in
the coil is 𝑉𝑖𝑡. Hence if this energy is converted into H calories of heat we have,
If the heat thus developed be measured by means of a calorimeter, then the
temperature of the calorimeter with its contents will rise from 𝜃1 0𝐶 𝑡𝑜 𝜃2 0𝐶.
Hence the heat taken up by the calorimeter and its contents is given by,
Where,
𝑚1= mass of the calorimeter
𝑚2= mass of the stirrer
𝑚3= mass of the contents in the calorimeter
𝑆1= specific heat of calorimeter
𝑆2= specific heat of stirrer
𝑆3= specific heat of the contents in the calorimeter
∆𝜃= (𝜃2 − 𝜃1)
From equation (1) and (2), we get
2. Apparatus:
 Joules calorimeter with heating coil
 Thermometer
 Rehostat
 Switch
 Stop watch
 A liquid of known specific heat
 Voltmeter
 Ammeter
 Weight box
 Balance
 Connecting wires
Lab Report Department of Physics Page 4 of
𝐽 =
Vit
H
… … … … . (1)
𝐻 = (𝑚1𝑆1 + 𝑚2𝑆2 + 𝑚3𝑆3 )∆𝜃 … … … … . . (2)
𝐽 =
Vit
(𝑚1S1 + m2𝑆2+ 𝑚3𝑆3 )∆ θ

4. 3. Procedure:
 Connections were made as shown in the figure 1. The calorimeter was cleaned
and it was weighted. Some liquid (water) was poured in the calorimeter and again
it was weighted. Hence the mass of liquid was determined.
Figure 1: Determining the value of J
 The heating coil was put in the calorimeter which just completely should be
dipped in the liquid. A thermometer was inserted in the calorimeter with the bulb
near the middle region of water but never the coil was touched. The calorimeter
was placed inside a double walled chamber.
 The circuit was closed temporarily to adjust the current of about 2 amperes.
Then the stop watch was started and the current was simulated and the liquid
was gone on stirring. The current ,voltage and temperature were recorded at an
interval of every time.
 When the temperature has been risen about 8°C, the current was stopped, time
was noted simultaneously for which the current flowed but the stop watch was
allowed to run on. The temperature will be further risen. The time was noted
from the beginning of starting the stop watch to the maximum rise of
temperature n. The temperature was recorded and the liquid was gone on
stirring as before.
Lab Report Department of Physics Page 4 of

5.  Then the calorimeter was allowed to go through the same length of time as it
has been rising in temperature and again the temperature was noted. The actual
loss in temperature, by radiation during the heating process was half of this fall
in temperature. This loss was added to the observed maximum temperature 𝜃2
to get the maximum temperature of the liquid.
Lab Report Department of Physics Page 4 of

6. Experimental Data:
Mass of the calorimeter, 𝑚1 = 70.8𝑔𝑚
Mass of the stirrer, 𝑚2 = 21 𝑔𝑚
Mass of the calorimeter and water, 𝑚 =227𝑔𝑚
Mass of water, 𝑚3 = 𝑚 − 𝑚1 = 156.2𝑔𝑚
Specific heat of calorimeter, 𝑆1 = 0.0909𝑐𝑎𝑙𝑔𝑚−1℃−1
Specific heat of stirrer, 𝑆2 = 1 𝑐𝑎𝑙𝑔𝑚−1℃−1
Specific heat of the contents in the calorimeter, 𝑆3 = 0.089 𝑐𝑎𝑙𝑔𝑚−1℃−1
Table1:Readings ofcurrent-voltage-temperature
No. of
observations
Time
(min)
Current, 𝒊
(amp)
Voltage V
(volts)
Temperature
𝟎𝑪
1 0 0 0 25
2 1 1.01 6.7 25
3 2 1.01 6.7 25.5
4 3 1.01 6.7 25.5
5 4 1.01 6.7 26
6 5 1.01 6.7 26
7 6 1.01 6.7 26.5
8 7 1.01 6.7 27
9 8 1.01 6.7 27
10 9 1.01 6.7 27.5
11 10 1.01 6.7 28

7. 12 11 1.01 6.7 28.5
13 12 1.01 6.7 28.5
14 13 0 0 29
15 14 0 0 29
16 15 0 0 29.5
17 16 0 0 29.5
18 17 0 0 30
19 34 0 0 28.5
20
Analysis and Calculation
Recordings oftime and temperature with radiation correction:
Initial temperature of calorimeter with its contents, 𝜃1 = 25℃
Final temperature of calorimeter with its contents, 𝜃2 =30 ℃
Time during which the current is passed, 𝑡 =12𝑚𝑖𝑛 =720 𝑠𝑒𝑐
Mean current during the interval, 𝑖=1.01 𝑎𝑚𝑝
Mean voltage during the interval, 𝑉 =6.7 𝑣𝑜𝑙𝑡𝑠
Rise of temperature, ∆𝜃′ = (𝜃2 − 𝜃1) = 5℃
Radiation correction, 𝜃𝑟=(
𝜃2−𝜃2
′
2
)=0.75℃
Corrected rise of temperature, ∆𝜃 = ∆𝜃′ + 𝜃𝑟=7℃+.25℃=7.25℃
Discussion:

8. The main objective of this experiment was to determine the value of the
mechanical equivalent of heat by electrical method. In the experiment, the reading
of temperature has been taken 25°C and 30°C, and the time was 12 minutes. After
completing the experiment, the value of mechanical equivalent of heat was
determined J = 5.15 J/cal. The temperature of the water in the calorimeter was read
up to the maximum calculation of the thermometer. The experiment was so long,
so there might be some problems in maintaining the time Other than Everything
was ok. We found the result very close to our expectation. So, we can say that our
experiment was successful.
References:
1. Practical physics (by Dr.Giasuddin Ahmed & Md Shahauddin)
2. Supplemental Modules (Physical and Theoretical Chemistry), chem.libretexts.org
3. Calorimeter – an overview, sciencedirect.com
4. Mechanical Equivalent of Heat – Energy Education, energyeducation.ca .