Math in… Batteries and Current
You might have noticed that most batteries have a plus sign on one end and sometimes also a minus sign on the other end. The ends are called electrodes. The positive end is the cathode and the negative end is the anode.
While batteries come in a variety of shapes and sizes, they always have a cathode and an anode.
In a circuit, negatively charged electrons travel from the anode to the cathode, creating current.
When people talk about electrical current, however, they usually say current flows in the opposite direction.
How current actually travels.
How we describe current traveling.
This is because scientists were experimenting with electricity long before electrons were discovered. They suspected electricity was somehow moving through a circuit like water through a pipe, which is why they used words like “flow” and “current”, but they had to guess the direction.
Benjamin Franklin knew it would be useful to pick a direction so that scientists had a common language. He decided electrical current flows positive-to-negative, and that’s the convention we’ve used ever since!
Electrons alternating their direction of travel.
A battery produces direct current (DC), meaning electrons always travel the same direction in the circuit.
When you plug something into your wall at home, however, it receives alternating current (AC). In an AC circuit, electrons quickly between alternate traveling one way and the other.
While numbers are also used to describe the strength of current in a DC circuit, in an AC circuit it is helpful to attach a sign to those numbers — positive when the flow is in one direction and negative when the flow is in the other direction.
Choosing which direction is positive and which is negative is completely arbitrary, but once we make a choice, we can calculate with it!
How can math be used to describe electricity?
