# Day 69: Can You Believe?

Thursday, 21 November 2013

When I lecture off the top of my head I make mistakes. Turns out EPE isn’t the same thing as voltage.

Can you believe I didn’t know the difference between electric potential energy and electric potential?

I’m just getting started on my electricity unit with kids and in a spare 20 minutes with two classes, I introduced a few ideas to lead us into circuits*.

The first was to develop an understandable definition of electricity based on their current understanding. I was happy when the kids got to the transfer of energy by charged particles. Yeah, I know that’s really more closely a definition of electrical current, but it’s good for a start and is certainly more understandable to freshmen than Wikipedia‘s.

After, I spoke of this energy transfer in terms of potential energy. The kids are already familiar with gravitational potential energy, so we talked in terms of electrical potential energy. I continued on to say this quantity is commonly known as voltage. After class, I confirmed my mistake. Sh!t. I was really trying to describe electric potential. Every source I’ve read makes a big deal that EPE and electric potential aren’t to be confused. Dammit. I just did that very thing.

Surely some of you have made such a dummy mistake. What’s yours?

Making a mistake because I didn’t really know the difference is the worst thing I think a teacher can do in the classroom. I think this officially makes me “that” teacher. Please don’t hold it against me too long.

One of the reasons my blog rarely is reflective is my own fear of being judged as an idiot. My post here is an attempt to break my own silence. Hey, we all make mistakes, some are careless errors we teachers know better about. The scarier errors are the ones we make because of a lack of or misunderstanding. It happens. I hate that someone out there is going to read this and say, “that Megan doesn’t know much about physics, she shouldn’t be teaching it.” I’m getting over that fear and instead trying to improve my understanding.

[Aside: When I told this story to my colleague, Ken, he suggested a better way to discriminate between the two is that while EPE is similar to GPE=mgh, electric potential is like gh. Did I tell that right?]

* Due to both time and scope concerns, I opted to teach circuits only this year. That means I’m cutting out electrical charge and Coulomb’s Law, which would normally be a part of my freshman-level course. I’ve never taught electric and magnetic fields in any detail.