25th - 26th SEPTEMBER 2019  |  OLYMPIA

The Physics of Falling Magnets in *Stranger Things* Season 3

Wired 09 Aug 2019 02:00

I think we need to have a talk about magnets in Stranger Things. Oh, you haven't finished Season 3 yet? Don't worry, this isn't a huge plot element, but it's still technically a spoiler. Just wanted to warn you.

Let's review the magnet parts of the plot. First, Joyce Byers (Winona Ryder) notices that her fridge magnets stop working and fall to the floor. This seems odd, so she decides to do some light reading of some advanced physics textbooks that she'd checked out of the library. Second, she stops by the house of the local science teacher, Scott Clarke (Randy Havens). They have the following interaction. Yes, I transcribed it—just for you.

Joyce: What is this again?

Scott: This is a solenoid. It's a coil wrapped around a metallic core and when electricity passes through it...

Joyce: It creates an electromagnetic field.

Scott: Exactamundo. Now for the fun part. Shall we?

Joyce: Yeah. [Scott turns on the solenoid] I ... I don't see anything.

Scott: Nope. You can't see it, but it's there, I assure you. Our very own Clark-Byers Electromagnetic Field. Pretty neato, huh?

Joyce: Yeah.

Scott: And this field affects any charged object in its vicinity.

Joyce: Just like my magnets?

Scott: Just like your magnets.

Joyce: OK, Why is nothing happening?

Scott: Oh, because our field is stable. But, if we reduce the current... [Scott turns off the current and the magnets fall off.]

Joyce: How...

Scott: The magnetic dipoles tried to orient according to the field, but—

Joyce: No, no, no. I mean how is this happening at my house?

Later: Scott: Theoretically speaking, I suppose some large version of this AC transformer could exist. A machine of some kind. But, in order to reach your house and downtown, gosh, that would take billions of volts of electricity and would cost tens of millions of dollars.

I know you have many questions. So, let's get to it.

What is a solenoid?

We are going to start with the simple stuff. Like Scott said, it's basically a coil of wire. If you add a solid ferromagnetic core (like iron), it will make a stronger magnetic field. I'm not too sure other metals will help that much. But you don't even need a solid core. It works with just air in the middle. The basic idea is that an electric current makes a magnetic field. If you wrap a wire into a single loop, the magnetic field from all the sides of the loop mostly align in the same direction to create a stronger field inside the loop. More loops (as in a solenoid) mean a greater magnetic field.

Oh, it looks like Scott wrapped the wire around something like a metal lunchbox. That's cool and everything (looks very MacGyver-like), but it has to have a solid metal core and not be hollow to have a significant influence on the magnetic field. One more thing.

Does a solenoid create an electromagnetic field?

No. Well, not always. OK, I'm actually not sure what an "electromagnetic field" actually is. I would interpret this as a region in space with both an electric field and a magnetic field in which the two fields can cause an electromagnetic wave. So, if you just have a constant electric current in the solenoid, you get just a static magnetic field. If there is an alternating current in the solenoid (as you would get by plugging it into an AC outlet), you would get a changing magnetic field due to the changing current. This changing magnetic field creates an electric field that also changes. The changing electric and magnetic fields are an electromagnetic wave.

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