What Is Electric Current? (Amperes)

Electric current is the amount of electric charge passing through a conductor per unit time; that is, the flow rate of charge (electrons). Its unit is the ampere (A), and it tells you "how much electricity is flowing" in a circuit.

How Does Current Form?

When there is a voltage (potential difference) between the two ends of a conductor, free electrons move under the influence of that difference. This orderly electron movement is what makes up the current. Without voltage there is no current.

The Unit of Current: the Ampere (A)

1 ampere means 1 coulomb of charge passing a point per second. In electronics you usually work with much smaller values:

Current Direction: Conventional vs. Electron Flow

There are two "direction" definitions: conventional current is taken to flow from the positive (+) terminal to the negative (−); in reality the electrons flow the opposite way, from negative to positive. Circuit analysis usually uses the conventional direction.

How Is Current Measured?

Current is measured by connecting the multimeter in series with the circuit; the current must pass through the multimeter. For connections and ranges, see What Is a Multimeter, and How Do You Use It? For the relationship of current with voltage and resistance, Ohm's law (I = V / R) is fundamental.

Common Mistakes

• Connecting the multimeter in parallel: plugging the probe in parallel when measuring current makes a short; current is always measured in series.
• Mixing up units: 100 mA and 100 A are very different; convert to amperes before calculating.
• Thinking of current as the "push": what pushes is voltage; current is the resulting flow.