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In this activity, you will use a model to explore how electric current heats up a wire.
Engage
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One way to make heat from electricity is to force electric charges through a wire. This motion of electric charge is called current. When you connect a circuit to a battery or a wall outlet, electric charge (current) flows through the wire.

One example of this is a light bulb. Here is a picture of a glowing bulb.
Study the filament (the small wire that is glowing). Would you guess that the bulb produces light energy, or heat energy, or both? light energy heat energy both light and heat
Write down other devices where electric current creates heat.

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When a wire, such as a light bulb, is connected to a battery, electric charges are pushed through the wire. When they bump into the atoms in the wire, they transfer some energy and the atoms heat up. It's a bit like trying to run through a crowd of people. You're sure to knock into someone along the way!

In this activity you will study a model of how this process works.

Explore
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Here is a picture from a model of a wire. The wire is in a circuit with a battery. A section of the wire is enlarged.

If you could look carefully at the enlarged part of the wire, you would see atoms (large dots ) and electrons (blue dots ). This is a model of what is going on inside the wire.


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The model will look like this. There are buttons to run it and graphs to show the effect of changing the voltage in the wire. Come back to this page if you forget how to run the model.
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Here is the inside of the wire.

The big circles represent atoms. The redder they are, the hotter they are. The small blue circles represent electrons. They have a negative charge. They are free to move in the wire. If voltage is applied, the left-hand end is negative and the right-hand end is positive. The electrons are pulled to the right.

Now try the model by clicking the go/stop button. Watch the path of one electron, using the watch one electron button. Describe the motion of one electron. What does it do when it hits an atom? It bounces off and goes in a new direction. Here is the key rule: every time an electron collides with an atom, it gives the atom a little bit of energy and loses some speed.
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This model was created using Netlogo. Go here to explore the model on your own.

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You can draw on the picture. Notice the electron's curved path as it is attracted to the right. Also notice how it bounces off the atoms.





Circle where the electron has hit an atom. Circle the hottest atom you can find. Take a snapshot of your drawing. This snapshot will be saved in your lab book. NaN NaN 377.0 -83.0
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This model was created using Netlogo. Go here to explore the model on your own.


Now test the effect of the voltage, which is how much force is pulling the electrons toward the positive (right-hand) end. Run the model. Note the atom temperature shown in the graph. Increase the voltage by moving the voltage slider. What happens to the temperature? Change the voltage back to zero. What happens to the temperature?
Take a snapshot of your experiment.
Explain
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1. What does voltage do to the electrons? 2. Look at your snapshot of the model. How does voltage affect atom temperature? greater voltage lowers atom temperature no effect greater voltage raises raises atom temperature greater voltage raises raises atom temperature 3. Why do you think so? What do the electrons need to do to heat up the atoms?
Elaborate
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This model was created using NetLogo. Go here to explore the model on your own.
Resistance is how much a material slows down the passage of electrons. Here is the same model, but there is a new slider called collision-chance . It is set to 0. Instead of bouncing off the atoms, the electrons go right past them. The wire has a low electrical resistance. Run the model and watch the graph. Start with zero voltage and increase the voltage. Increase the collision-chance. How does the motion of the electrons change?
When you increase collision-chance, what happens to the temperature of the atoms? The temperature goes up. The temperature goes down. The temperature doesn't change. Why do you think this happens? Take a snapshot.
Evaluate
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Draw your own picture of what it looks like inside a wire that is being heated up by electricity. You can use the electron stamp (blue) and the two atoms stamps -- black for cold and red for hot. Take a snapshot of your drawing. Explain how resistance makes it possible for the electric current (moving charges) to heat up a wire.
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Congratulations! You have completed this activity. Did the computer model in this activity help you learn about electricity? Yes Somewhat No How well were you able to use the drawing tools? I did not draw using the computer. They were easy to use. Some were hard to use. Most were hard to use.
How does electricity make wires hot?