The document summarizes an experiment to determine the efficiency of converting electrical energy to thermal energy. A hot plate was used to heat water, and temperature over time was recorded. The expected efficiency was 100% based on the law of conservation of energy. However, the measured efficiency was only 43.8%, likely due to random errors such as water evaporation and unstable thermometer readings. Improving the experimental method by limiting evaporation and taking continuous temperature measurements could help reduce errors.

1. Energy Conversion Practical
Introduction
When energy is used to do work, it usually changes into a different form of energy. This
experiment is about electrical energy converting into thermal energy. An example od electrical
energy converting into thermal energy is when water is heated on an electric stove. The energy
used to start the oven is electrical energy. During the process of boiling water, the electrical
energy becomes thermal energy. According to the law of conservation of energy, the initial
energy should equal final energy. In this experiment, the initial energy is electrical energy and the
final energy is Thermal energy. Thus, the amount of electrical energy should equal the amount of
thermal energy, although this was not true in this experiment because of random errors. In this
experiment the formula VIT was used to find electrical energy, and the formula mc(delT) to find
the thermal energy (delT = change in Temperature). The efficiency was calculated using the
formula
Efficiency= 100% (output)/input
The output is the thermal energy and the input is the electrical energy. The efficiency was off
because of random errors. The time that the water boils and the Temperature of the water are the
only variable. The mass of the water, specific heat constant, voltage and current are all constants.
The primary goal of this experiment is to determine the efficiency of converting energy from an
electrical form to a thermal form. The efficiency was expected to be very close to 100%
according to the law of conservation of energy.
Design
Research Question: What is the efficiency when electrical energy is converted into
thermal energy?
Independent Variable: the time the water is heated up for
Dependent Variable: the temperature of the water
Controlled Variables:
1. Mass of water
2. Voltage
3. Current
Description: A hot plate was plugged into an outlet and had 230.0 V and 4.0 A. A beaker
of water was placed on the hot plate; the mass of the water being 96.39 g. A thermometer
was inside the beaker, which was held in place by a retort stand. The hot plate was turned
on and the time was recorded via a continuum and processed into a computer.

2. A Picture of The Experiment

3. Raw Data
Time (± 0.5 sec) Temperature (± 0.5 °C)
0.0 31.0
30.0 37.0
60.0 42.0
90.0 47.0
120.0 53.5
150.0 61.0
180.0 70.0
Processed Data
Efficiency = 100% (output)/input
Output = thermal heat
Thermal Heat = mc(delT)
delT = change in Time
Input= electrical energy
Electrical energy= VIT
Efficiency= 100% (mc(delT))/ VIT)
delT/t = slope of the Temperature/ Time graph= .2101
c= 4.1813
m= 96.30 g± .01
delT/ t= 0.2101 ± .0001 C
I= 4.0 A±.1
V= 230.0 V±.1
T=
Sample Calculation
Efficiency = 100% ( delT/T){(96.30) (4.1813)}/ (230.0) (4.0)
Efficiency = 100%(.2010) {(96.30) (4.1813)}/ (230.0) (4.0)
Efficiency = 43.8%
* the uncertainty is too small too make a difference or change the answer
Conclusion
In a perfect world with no errors the efficiency of the conversion of electrical to thermal
energy should be 100% because the thermal energy should equal the electrical energy.
Taking into account random errors the efficiency should have been in the range of 90%-
100%. The results for the efficiency were extremely inaccurate at 43.8%. A conclusion
that can at least be drawn from the experiment is that although efficiency is supposed to

4. be 100%, it will almost never quite reach that number because of random errors, which
are results of an imperfect world. By evaluating the slope of the graph, one can see that
the relationship between the change in Temperature and time is linear and that the slope
of the graph of Temperature versus time can be substituted into the derived equation of
efficiency (100% (mc(delT))/ VIT) for delT/ T. Without the slope of the Temperature
versus time graph efficiency would be very difficult to calculate.
Evaluation of Random Errors
The experiment’s results were quite different then what they were expected to have been
or than what they should have been according to the law of the conservation of energy
because if both energies are equal the efficiency result equals 100%. The inaccuracy is
largely due to random errors.
1. One random error that happened in this experiment was a loss of some of the mass of
water when it was heated because some of the mass was evaporating. A difference in
mass would affect thermal energy and thus would affect the efficiency results. To fix
this a piece of cardboard or thick material could be place over the beaker to prevent
evaporation. A whole would have to be poked into the cardboard just small enough
so that the thermometer could be inserted in.
2. Another random error was trying to measure the change in Temperature as related to
time. At first, this was tried by measuring specific times and temperatures separately
but this affected the results because the starting Temperature was different each time
and measurements were affected by the previous experiments, and it was hard to
calculate. To fix this a continuum was used so that the temperature and time could be
related in a graph and the change in Temperature divided by the time could be
measured by taking the slope. This also led to better accuracy and precision.
3. The last random error was when someone held the thermometer to measure the
temperature of thewater, it was unstable and difficult to get an accurate reading in a
short time. To fix this a the thermometer was attached to a retort stand.