Introduction: (Initial Observation)
I was looking at electric heater and wondering how does it get hot? To use the electric heater we usually plug it to the electricity and turn a knob. It gradually starts to get hot.
Electricity and heat are two different types of energy. Does an electric heater convert electrical energy to heat energy? How does it do that? If electricity produces heat, why all the electric wires are not hot? and why the air conditioning unit creates cold air?
Adult supervision and support is required for the experiments. Only use battery. Home electricity is dangerous and must not be used for such experiments.
Information Gathering:
Find out about electricity and how it works. Read books, magazines or ask professionals who might know in order to learn about the electric heater and other electrical equipment that produce heat. Make a list of electrical devices that produce heat. Keep track of where you got your information from.
Following are some web based information:
While browsing the Internet I noticed that there are many products in the worlds market that use electricity to create heat. One of the smallest of these products is a water heater used to make hot water right inside the mug.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to determine if electricity can directly produce heat. Different material will be tested to see if the flow of electrons (electric current) in them will produce heat.
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable is the material that may produce heat when electric current passes through them. (Different wires and different liquids)
Dependent variable is the temperature of such material.
Controlled variables are the electricity source (battery) and experiment procedures.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
I think that electricity will create heat if it goes through narrow or thin wires. My hypothesis is based on my observation of light bulbs that have a thin wire inside (called filament). The thin wire inside the light bulb gets so hot that it produces light.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Experiment 1:
In this experiment you connect the ends of a thin wire to the poles of a 6 volt battery to determine if the wire gets hot.
Procedure:
- Get about 1 foot thin wire of any type. You may pull out one strand of a stranded cable for this experiment.
- Wrap the wire around a pen to make a coil. Make the loops next to each other or as close as possible, but don’t overlap them. Remove the pen and use the spring shape coil of thin wire for this experiment.
- Secure the ends of the wire with nails or screws on a wooden board.
- Connect a regular thick electrical wire from one end of the wire coil to one pole of a 6-volt battery.
- Run another regular thick electrical wire from the other end of the wire coil, to the other pole of the battery, but don’t connect it now.
- Insert the bulb of a glass thermometer in the coil and read the temperature.
- Place another identical thermometer away from the coil as a control experiment. Read the temperature in control thermometer as well.
- Record the initial temperatures of both thermometers.
- Connect the last wire to the open battery pole and observe the wire for one minute. Record your observations. Read the thermometers at the end of one minute and record the results.
- Disconnect the last wire from the battery to open the circuit.
Notes:
The wire that you use for coil or spring must be very thin. It is best if you use a tungsten wire similar to those used to make the filament for light bulbs. Another good option is using chrome wires. The problem is that these wires are not easily available. So your last choice is using copper or aluminum wires. Most soft electrical wires are made of many strands of thin copper wire. If you remove the plastic coating, you will be able to remove one strand of thin wire for your experiment. You can buy wires from electrical suppliers or hardware stores.
The idea is that electrons have a hard time passing through a thin wire, so they rub against each other and against the wire and that creates heat. Like when you rub your hands to each other. Friction creates heat.
You can not use a metal thermometer for this experiment. The one shown in the picture is a room thermometer (from a dollar store) that I separated it’s back plate.
If the battery is strong enough and the wire is very thin, wire may get very hot and burn. In this case you have an obvious result and you do not need to use a thermometer at all.
Excess amount of heat may permanently damage the thermometer.
Experiment 2:
In this experiment you pass an electric current through water or a salt water solution to determine if electricity can increase the temperature of liquid.
Procedure:
Remove insulation from one inch of the ends of a pair of wire. One end of this pair goes to the poles of a 6 volt battery. The other end of this pair must enter water or a salt water solution without ever touching each other.
A thermometer in water can show any temperature increase.
To make sure that the wires do not touch each other inside the liquid, use a tape or rubber band to secure the wires on the sides of a pen or wood dowel before you insert them in water.
This experiment will release a small amounts of hazardous gases such as Hydrogen and Chlorine.
Experiment 3:
Use the results of experiment number 1 to make a foam cutting tool.
Foam cutting tools are hot wires mounted on an arc or on a table. Most foam cutting tools have a transformer that can produce different voltages. You adjust the voltage based on the amount of heat that you need on your cutting tool.
In this experiment you will use a 6-volt battery instead of a transformer.
Procedure:
Use a few pieces of wood to construct a U shape structure. Insert one regular screw and one eye screw on the ends of the U. Also insert another screw on the side of U structure.
Run a very thin wire (heat element) from the screw on one end of the U, pass it through the eye screw on the other end, and then use a spring to connect this end to the
screw on the side. Spring will keep the thin wire stretched even after it gets hot and it expands. Now connect two regular wire from two regular screws to the poles of a 6 volt battery. Heat element will get hot enough to cut the foam.
If the heat element wire is too thick, it will not get very hot and you can not cut the foam. A similar problem happens if the battery is too weak.
Almost any thin wire can be used as heat element; however, copper and iron burn and break fast.
Nickel-chromium alloys or tungsten alloys are often used for this purpose because they last longer. Tungsten is the same metal use to make the filaments of light bulbs.
Battery life is limited. Most foam cutting tools use a transformer to convert the city electricity (110 volts or 220 volts) to safe low voltage electricity of about 5 volts for the heat element.
In this image we are using an old computer power supply for our foam cutting tool. Computer power supply gets the home electricity and converts it to DC (Direct Current) 5 and 12 volts. Black wires are for ground. Red wires are 5 volts. Yellow wires are 12 volts. We used one red and one black wire to have 5 volts. Not everyone has access to an old computer power supply. Small 6 volt transformers can be purchased from local hardware stores and they usually work well.
Materials and Equipment:
Following is a suggested list of material for experiment number 1.
- Large 6-volt battery known as lantern battery
- 2 identical glass thermometers
- Very thin wire
- Wooden board
- plastic rod or tube (such as a pen) or wood dowel
- Test tube
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
No calculation is required for this project.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
