They're made with TWO coils of wire wrapped near each other... |

In my zapper, the wall transformer's first coil (called the "primary") sees alternating current at around 117V. It reduces this to only 12V in the other coil (called the "secondary").

Transformers can be described with these two equations:

**Voltage
primary / Voltage secondary = # turns primary / # turns secondary**

**Current
primary * Voltage primary = Current secondary * Voltage secondary**

TERMINOLOGY:

**transformer:**
device that changes voltage and current in a circuit

**current:**
amount of electric charges that flow in a wire

**amperage:**
the rating unit of current

**wall
transformer:** just a transformer that can be plugged into a wall outlet

**turns:**
how many loops a wire makes in a transformer

**coil:**
many loops of wire, sometimes wrapped around metal

**alternating
current:** current that changes direction (like your wall outlets provide)

**direct
current:** current that flows in only one direction (like a car or flashlight
battery provides)