If you have been following my blog, you might know already, that I love a good hands-on experiment served with the good ol’ inquiry. These static electricity experiments I’m going to explain are just that – prompted with a question, they awe students into wanting to inquiry the nature of hair standing to all sides, balloon floating on the ceiling and maybe even waterbending with a comb. So let’s dive into the physics behind these fascinating experiments.
This experiment might be a tale as old as time but it almost every time catches childrens’ curiousity and interest. They just WANT to do it themselves. See how their hair stands apart. Laugh at each other. Maybe even try to put the balloon up to the ceiling or the wall. I know that I always did. And still do, as a matter of fact. But what exactly is happening when I rub the balloon over my head? Sometimes I can even hear a crackling, like electricity.
And it’s something like that. The phenomenon is called static electricity and it’s electrons moving somewhat freely in the material. When a rubber balloon is rubbed against human hair, electrons are transferred from the hair to the balloon, giving the balloon a negative charge, and leaving the hair with a positive charge. The hair is attracted to the balloon, because the materials have opposite charges. When the balloon is pulled away from the hair, the positive charge of the hair makes the hair stand out, because the positive charge on the individual hairs causes each hair to repel the other hairs. That’s why you end up looking a little like Albert Einstein.
And putting the (now negatively charged) balloon to a ceiling or a wall brings up the next question: How does the balloon stick to the wall or ceiling? There is no glue, no string and the wall is not positively charged like our hair is at the moment (still looking funny, huh?).
This is where the scientific reasoning comes in. Remember how I said that electrons are moving somewhat freely in the material? That’s how they were able to transfer from our hair to the balloon anyway. And it’s the same in the ceiling or the wall. The negatively charged balloon repells the electrons (which are negative charges) in the wall, leaving only the positively charged ions (ions are charged atoms or molecules) behind. These are attracted to the negatively charged balloon but since the wall cannot move, the balloon simply sticks to the wall.
Over time, the electrons will wander from the balloon to the wall, making the balloon fall to the ground. It will not stick to the wall forever. But still, it makes for a great demonstration and since we can’t see what’s happening in the wall or ceiling, we need to induce what might happen from our previous experiments.
There are several more cool static electricity experiments like bending water with a balloon, using a Van de Graaff generator or demonstrating a jacob’s ladder and its spark gap. These take up a little more explaining than just simple positive and negative electrical charges but are worth a look at in science classrooms because they make for amazing demonstration experiments. Especially with regards of the simple static electricity experiments I just presented to you, the topic can be embedded as sort of a spiral curriculum and students can fall back on their knowledge on charges and static electricity.