Voltage, Current & Resistance

Voltage (measured in volts, symbol V) is the electrical pressure that pushes electrons through a circuit—think of it like water pressure in a pipe. A battery's voltage rating (like 12V) tells you how much pressure it provides. Current (measured in amps or amperes, symbol I or A) is the actual flow of electrons moving through the circuit, like the amount of water flowing through a pipe. The more pressure you have, the more water (or electrons) flows—unless something blocks the flow.

Resistance (measured in ohms, symbol Ω or R) is the opposition to current flow, like a narrow section in a pipe that restricts how much water can pass. A thick copper wire has low resistance; a thin wire or a resistor component has high resistance. Materials, length, and temperature all affect resistance.

Think of a simple battery-powered flashlight: the battery provides voltage (pressure), the filament provides resistance (opposition), and current flows from the battery through the filament and back. Without resistance, current would flow uncontrolled and damage the circuit. Without voltage, nothing happens. These three quantities are always related.

On the ASVAB Electronics Information section, you'll solve problems using Ohm's Law. Understanding how these three quantities interact is the foundation for everything that follows.