We've been taking a bit of a respite over the holidays and spent most of the time in Reno, where my in-laws live. The weather, which is pretty much always better than Michigan in winter, was absolutely gorgeous - mostly 40s and 50s. As is typical of the Reno climate, it was also very dry and we had to get used to the constant shocking we were giving each other from the static electricity we generated. (Don't get me wrong - I'll trade higher levels of static electricity for warmer weather ANY day!) Inspired by this, when we returned home the girls and I worked on an activity that examines which type of fabric creates the most static electricity. Winter is a great time to do this activity as the lower humidity should make the experiment more successful.
- inflated balloon
- variety of fabrics (we used wool, polyester, cotton, tulle, fleece and flannel)
- acrylic rod
- paper hole punch
- piece of computer paper - punch out approximately 10 dots/type of fabric)
|Sculpey Acrylic Roller|
I am a wannabe-sewer, so I have a fabric stash to pull from but if you don't have fabric lying around you could certainly use clothes made from different materials or check the remnant bin at your local fabric store. The acrylic rod we used was one of those 3/4" thick clay rolling rods like the picture to the right. I imagine an acrylic drink stirrer or one of those glitter wands would work just as well. In addition, glass works very well so if you can find any glass rods then definitely try that!
Part I: Demonstrating Static Electricity
This is a very basic demonstration of static electricity that I can almost guarantee everyone has done before, but kids get a kick out of it every time. Take a balloon and rub it against your head until you have generated enough static electricity to make your hair stand on end. Have your child slowly pull the balloon away from their head and observe what happens. It's fun to have a mirror around when doing this. If its an especially dry (low humidity) day, try sticking the balloon to the wall. (You could also try this in a steamy bathroom and compare the results to just being in normal climate of your house.) Tell them a bit about the static electricity that is created when two materials are rubbed together causing one to take a slightly positive charge and the other to take a slightly negative charge. The difference in charges will cause the materials to slightly stick together.
Part II: Fabric and Static Electricity
Discuss with your child any examples of times they've experienced static electricity; it may be a shock from touching something when its dry out (especially after running around on a carpet while wearing socks). Or maybe they've seen the sparks generated from fleece pajamas rubbing against their bed sheets (my girls LOVE this!). Show them the different types of fabric you have gathered and have them predict which fabric will create the most static electricity.
Start by placing 10 punched paper dots on your work surface. They should be fairly close together but not touching.
Select the fabric that you want to test to start and have your child hold the base of the acrylic rod and quickly rub the rod with the fabric a number of times. We did 50, but you may need to experiment a bit depending on the type of rod and fabric you are using and the level of humidity. Alternatively, you could rub it for a certain amount of time for each fabric.
Remove the fabric and slowly pass the rod over the paper dots and then observe how many dots were picked up by the rod. Try not to touch your work surface - you may need to help guide their hand to prevent this from happening. If it does touch, its possible that the small charge generated will discharge. It happened several times to us but I don't think it made a huge difference in the results.
Record how many dots were picked up by the fabric, replenish the dots so that you again have 10 to start with and then do the same thing with your next fabric. Make sure to rub the rod for the same number or amount of time for each fabric. We used the opportunity to practice our graph making. First we lined up each dot that stuck to the rod under each of the fabric samples, and then we made a simple bar graph showing the results.
Have your child evaluate the results, using the data from the graph if they made one. Ask them which fabric(s) created the most static electricity and which created the least. See if they can think of other ways to test for static electricity.
Static electricity is created when two materials are rubbed together and one of the materials loses some of its electrons to the other material, causing it to become charged. This phenomenon is known as the triboelectric effect. The level of charge depends on many things including the humidity, surface roughness and the materials. Some materials are more likely to become positively charged while others are more likely to become negatively charged. In addition, depending on how easy it is for the material to gain or lose the electrons, the material may have a stronger or weaker charge. Thus, materials can be placed in an order, known as the triboelectric series, in which the materials at the top are likely to have a strong positive charge and the materials at the bottom are likely to have a strong negative charge. (The image at the righ is a simplified version of the triboelectric series.) The farther apart the two materials are on the list, the greater the amount of static electricity that will be created when they are rubbed together.
We love the Magic School Bus series and the Magic School Bus and the Electric Field Trip book does a good job with a basic introduction to electricity, including a bit about static electricity.
For older kids, try doing multiple trials and have them record their results on a data chart. They should average each of their trials and then they could rank the materials based on their data. Finally, they can compare the results they received to a table of known Triboelectric values (like this one) and evaluate their results. You could also repeat on different days, taking note of the humidity levels, and see if that makes any difference in the results.
Other common household materials besides fabric can be used. Try aluminum foil, plastic wrap, computer paper, adhesive tape, paper napkins, etc.