Text reads: The Mysteries of Life with Tim and Moby
Moby stands on the front step of a house and rings the doorbell. Cassie opens the door.
CASSIE: Um, can I help you?
CASSIE: Wait a second. I know you. You're that Moby kid who hangs out with Tim.
CASSIE: Oh, right. Because you guys do that movie thing.
Moby hands Cassie a sheet of paper. Cassie reads from a typed letter.
CASSIE: Dear Cassie and Moby, How do batteries create electricity? From, Jack M. Hi, Jack. You probably know that electricity is a type of energy. That's a property of matter, like its size or its mass.
An animation shows a small red ball with its size and mass being measured with a ruler and a scale.
CASSIE: Energy is what causes matter to move or change, like a ball dropping to the ground.
The ball falls through the air.
CASSIE: Or electricity, it's a stream of tiny, moving particles.
An animation shows an electrical circuit in which a battery provides power to illuminate a light bulb.
CASSIE: Or heat, which is actually just the vibration of atoms.
An animation shows a wooden match igniting.
CASSIE: These are all examples of kinetic energy, the energy of motion.
Cassie and Moby are seated at a table. Cassie leans toward Moby, who is drinking a glass of orange juice.
CASSIE: Pssst. How am I doing?
He winks at her.
CASSIE: Okay, so objects at rest have energy, too. It's called potential energy.
An image shows a red ball sitting motionless on a flat surface.
CASSIE: You can think of it as kinetic energy that's stored due to an object's position. Like if I pick up this ball.
There is a ball on the table in front of Cassie and Moby. She picks it up and holds it above the surface of the table.
CASSIE: Up here, it has more potential energy than it did on the table. Put another way, its new position makes it less stable.
Three bars appear. One indicates that the ball has a high degree of potential energy. Another indicates that the ball has a low degree of stability. The third indicates that the ball has no kinetic energy.
CASSIE: Dropping it converts that stored energy into motion. It gains kinetic energy during its fall, loses potential energy, and gains stability.
Cassie lets go of the ball. As it drops, the bar graph indicates the potential energy, stability, and kinetic energy changes Cassie describes. The ball hits the table and bounces.
Moby frowns. He is holding a flashlight battery.
CASSIE: Man, you're kind of impatient, you know that? My point is, a battery doesn't actually create electricity. It converts it from chemical energy. That's a form of potential energy stored inside all matter.
An animation shows a cross-section of a flashlight battery. A glowing light inside represents its stored energy.
CASSIE: Well, it comes from the charged particles that make up an atom. Specifically, the negative electrons that surround the nucleus.
An animation shows the structure and activity of an atom as the electrons move around the nucleus.
CASSIE: It takes a lot of energy to keep those electrons so close together, because like charges repel each other.
An animation shows two of an atom's electrons staying near each other, despite their like charges trying to force them apart.
CASSIE: Freeing them from their orbit will release that potential energy.
One of the electrons leaves its orbit, releasing energy as Cassie describes.
CASSIE: Well, it happens during chemical reactions. That's when atoms combine or break up to form new substances. Lots of reactions involve a swap of electrons. A battery is a device that gets in the middle of that process.
An animation shows two smiling atoms attempting to exchange electrons. A battery comes between them and blocks the exchange, grabbing electrons for itself.
CASSIE: It redirects the electrons into a stream, better known as a current, or electricity.
The battery directs its stolen electrons into an electrical current, as Cassie describes.
CASSIE: Pretty much every battery has the same basic parts. There are two metal terminals, the anode and the cathode. They're separated by a thin material that blocks electrons. And they're soaked in an electrolyte, a mix of liquid chemicals. A collector provides a way for electrons to leave the battery.
An animated, labeled cross-section of a flashlight battery shows all of the parts described.
CASSIE: Let's start with the anode. Atoms in the metal react with the electrolyte. They dissolve into it and lose some of their electrons in the process. That loss turns the dissolved atoms into positive ions, charged particles. They travel to the cathode, leaving the electrons behind.
An animation shows the atoms reacting with the electrolyte and traveling from the anode to the cathode.
CASSIE: Yep, all those negative electrons are pushing against each other, creating instability. The more of them there are, the higher the voltage. That's the electrical form of potential energy.
A bar graph illustrates the increase in voltage, or potential energy, as the electrons move around.
CASSIE: To release the energy, you need to provide a circuit, a path for the electrons to reach the cathode, because they can't get through that separator. The wiring inside an electronic device gives them the path they need. Along the way, the electrons transfer some of their energy to the device.
An animation shows a cross-section of a flashlight, demonstrating how its on-off switch completes the battery-light circuit that illuminates the bulb. Bar graphs indicate the levels of kinetic energy and potential energy as the flashlight operates.
CASSIE: After that, the electrons flow into the cathode. They trigger a chain of chemical reactions between the cathode, the electrolyte, and positive ions from the anode. The exact reactions vary with the type of battery. But no matter what, they depend on a steady input of electrons.
An animation illustrates the reactions Cassie describes.
CASSIE: Good thing the anode is an electron-pumping machine, am I right?
Cassie holds a hand up to Moby for a high-five. Moby crosses his arms and looks away from her.
CASSIE: Come on, man. High-five.
Moby quickly high-fives her, then looks away again.
CASSIE: Yeah, batteries eventually go dead. It happens when they run out of the chemicals needed for a current.
An animation shows a cross-section of a flashlight's battery as it runs out of energy. Graphs show that there is no kinetic energy and no potential energy.
CASSIE: It's like the ball after it drops to the ground.
A ball is standing still on a flat surface next to the dead flashlight.
CASSIE: The potential energy has changed into kinetic energy. The system is now more stable, with less energy overall.
CASSIE: In these old-style flashlight batteries, that's the end of that.
An image shows a cross-section of a flashlight with a dead battery.
CASSIE: But batteries in cars, phones, and laptops are rechargeable.
An animation of a smartphone shows a flashing battery symbol, indicating the need for a recharge.
CASSIE: When you plug in the charger, it runs a current in reverse. Electrons are pulled away from the cathode and pushed into the anode. That reverses the chemical reactions. It's like the battery itself becomes the electronic device.
An animation shows a battery recharging and electrons moving from the cathode into the anode as Cassie describes.
CASSIE: It absorbs the kinetic energy of electricity and converts it into potential energy.
Bar graphs show kinetic energy converting into potential energy.
CASSIE: So, uh, that's my spiel on batteries.
She looks toward Moby.
CASSIE: What do I get paid for these things, anyway?
Moby holds up a T-shirt with a picture of a flashlight battery on it.
CASSIE: You have got to be kidding me. You know how much my time is worth?
CASSIE: Six bucks an hour babysitting, dude.
There is a short, silent pause. Cassie crosses her arms.
CASSIE: Just give me the shirt.