This is an excellent hands-on activity in which the students repeat a bit of engineering history. With just one six-volt lantern battery (or alternately, four 1.5-volt D cells in series), students can cause a filament of wire to glow. The list of materials for this activity is a bit greater than for some of my other activities, but it is worth taking the time to assemble them.
At a minimum, you should have batteries (in battery holders for D cells), test leads, and a variety of wires to try as filaments. I found some very fine copper wire within some of out broken test leads, and that was very useful for filaments. A second successful filament was fine strips of aluminum foil cut with scissors as thin as you can get it. Our brightest filaments were made from 28 gauge steel and galvanized wire, which I show in one of the photos. Another source of fine wire was braided cable for hanging pictures unbraided to single strands. I have included a photo of all of the filaments we have used. The complete list of materials includes a few other common materials that help (paper or plastic cups, and tape).
Note that a $10 lantern battery has the power to make glow more types of filaments, but the potential for excessively heating filaments and test leads increases as well. The D cells allow students to vary the voltage, and some of the finest filaments worked best with just 4.5 volts (3 D cells). Use your discretion in assessing your students' ability to work carefully with these materials. The potential for minor burns from glowing filaments is real. I have done this activity with third and fourth graders without anyone getting hurt, but the potential for not following directions may increase with age.
I explain to my students at the beginning of the year that, as they show me they are ready for real science materials and are able to use them responsibly, they will get to do more of the experimenting and investigating on their own. This activity would work fine with you demonstrating the different filaments, and it will go more quickly. I strive to let students have hands-on experiences with materials, but you may need to limit this due to time or safety constraints.
The lab is at least three hours of work, but more likely will occupy the students for twice that or more, depending on how long you want to let them explore. There are many associated activities you could add. Students could study the historical context of the electrification of the United States, they could learn more about the battle between Edison and Tesla over alternating and direct current, and they could investigate the effects of the light bulb on productivity at home and work.
The directions are included within the text of the lab, for the most part, but here is a summary. Students first describe and sketch a simple circuit with a selected filament to try. Then they identify problems with it and suggest modifications.
I think many of the filaments fail simply because the heat caused by the current is sufficient to melt the wire. Modern bulbs use a tungsten filament which has a higher melting point than copper or steel (two metals you will be able to find in varying wire gauges).
In this activity, students are asked to identify variables. The most important being the type and length of filament and the number of batteries (if using D cells). They are asked to identify problems and brainstorm solutions. There is a chance to discuss the role of oxygen in the failure of the lights, and there are several summary questions at the end.
I have included the rubric I use with this activity. Everything comes in both editable Word files and PDF files. You can edit the Word files to fit your use.
As a related demonstration, that I typically do as the students watch, rather than let students try, you can brainstorm ways to limit the oxygen available to the filament. There are two ways I have tried to limit the available oxygen. The first is to place a jar over the filament and burn a birthday candle inside the jar to use up most of the oxygen. You may want to seal the base of the jar with clay or Play Dough. A second way is to place the filament within a jar with the opening facing up and then fill the jar with carbon dioxide, either from a cylinder or generated with baking soda and vinegar. Try to lead the students to suggest their own solutions before demonstrating these.
I have not had luck with either of these methods resulting in increased filament life. Again, I believe this is because the filaments are melting, not burning. This is not to say that this is not a useful addition to the activity. Just because an activity does not turn out the way you anticipated does not mean it is not worthwhile. Just know that it may not be a factor in the life or the filaments. If you wish to skip this part of the activity, simply omit the fourth and fifth pages of the lab. The questions on page six are still applicable to the students’ efforts making a glowing filament.
If you want to demonstrate metal burning, you may show the students 0000-grade steel wool burning. You may light it with a match, but it will also burn if shorted out using a 9-volt battery. This is mentioned in the text of the lab.