What Is Electric Current? Amps, Flow, and How It Works

Electric current is the flow of electric charge through a conductor. It is measured in amperes (A), commonly called amps. Current is what makes circuits do useful work — it lights LEDs, spins motors, and powers microcontrollers. Without current flow, a circuit does nothing.

How electric current works

Current flows when a voltage source (like a battery) creates a difference in electrical potential across a circuit. This potential difference pushes electrons through the conductor from one terminal to the other, creating a continuous flow of charge.

Using the water analogy: if voltage is the water pressure, current is the actual flow of water through the pipe. Higher pressure (voltage) pushes more water (current) through the pipe, unless the pipe is narrow (resistance is high).

The relationship between current, voltage, and resistance is defined by Ohm's Law:

I = V / R

Where:

• I = current in amperes (A)
• V = voltage in volts (V)
• R = resistance in ohms (Ω)

This tells us that for a given voltage, more resistance means less current, and less resistance means more current. Calculate any of these values with our Ohm's Law Calculator.

The ampere explained

One ampere is defined as one coulomb of electric charge passing a point in one second. A coulomb is approximately 6.24 × 10¹⁸ electrons. In practice, most electronics work with much smaller currents:

Conventional current vs electron flow

There are two ways to describe the direction of current, and this confuses many beginners:

• Conventional current flows from positive (+) to negative (−). This is the standard used in circuit diagrams, textbooks, and engineering. It was established before scientists discovered that electrons are the charge carriers.
• Electron flow goes from negative (−) to positive (+). This is the actual physical direction electrons move in a conductor.

Both conventions describe the same circuit and produce the same results in calculations. All schematics and formulas on this site use conventional current direction (positive to negative), which is the universal standard in electronics.

DC current vs AC current

Current comes in two forms depending on how the voltage source behaves:

Direct current (DC)

DC flows in one direction only, at a steady rate. Batteries, solar panels, USB ports, and Arduino boards all provide DC. When you connect an LED to a 9V battery, the current flows continuously from the positive terminal through the LED to the negative terminal.

Alternating current (AC)

AC reverses direction periodically. Wall outlets provide AC — in North America at 60 Hz (the current reverses direction 120 times per second), in Europe at 50 Hz. AC is used for power transmission because it can be easily stepped up or down using transformers.

For a deeper comparison, see our AC vs DC guide.

Current in series and parallel circuits

How current behaves depends on the circuit configuration:

Current in a series circuit

In a series circuit, current is the same through every component. There is only one path for charge to flow, so the same amount of current passes through each resistor, LED, or other component. If 20 mA flows through the first resistor, 20 mA flows through all of them.

I_total = I₁ = I₂ = I₃

Current in a parallel circuit

In a parallel circuit, current splits between branches. The total current from the source divides among the parallel paths, with more current flowing through lower-resistance branches. The branch currents add up to the total current.

I_total = I₁ + I₂ + I₃ + ...

This is Kirchhoff's Current Law: the total current entering a junction equals the total current leaving it.

How to measure current

Current is measured with an ammeter or a multimeter set to current mode (A or mA). Unlike voltage measurement (which is done in parallel), current must be measured in series — you break the circuit and insert the meter so that all current flows through it.

Steps to measure current

1. Turn off the circuit.
2. Set your multimeter to the appropriate current range (A for high current, mA for small current).
3. Break the circuit at the point where you want to measure current.
4. Connect the meter in series — red probe on the side closer to the positive terminal, black probe on the other side.
5. Turn the circuit back on and read the current value.

Warning: Never connect an ammeter in parallel across a component or voltage source. An ammeter has near-zero internal resistance and will create a short circuit, potentially blowing the meter's fuse or damaging the circuit.

How much current do common components use?

Knowing these values helps you choose the right power supply, wire gauge, and protection components for your projects. When using LEDs with an Arduino, you need a current-limiting resistor — use our LED resistor calculator to find the right value.

Current and safety

It is current through the body, not voltage alone, that causes injury. However, higher voltage can push more current through the body's resistance (~1,000–100,000 Ω depending on conditions):

• 1 mA: Barely perceptible tingling.
• 10–20 mA: Painful shock, possible muscle lock ("can't let go").
• 100–200 mA: Potentially fatal (ventricular fibrillation).
• 1+ A: Severe burns and internal damage.

For hobby electronics at 5V–12V DC, the risk is very low. Mains voltage (120V/230V AC) is dangerous and should only be worked on by qualified people.

Common mistakes with current

• Measuring current in parallel. Connecting an ammeter across a component creates a short circuit. Always measure current in series.
• Exceeding a component's current rating. Every LED, resistor, and IC has a maximum current rating. Exceeding it causes overheating or failure. A standard LED rated for 20 mA will burn out if you push 200 mA through it.
• Forgetting current-limiting resistors. LEDs have very low forward resistance. Without a series resistor, current through the LED will be far too high. See our LED wiring guide for proper connections.
• Confusing current direction. Conventional current goes from + to −. Electron flow goes from − to +. When reading schematics and datasheets, always use conventional current.

Summary

Electric current is the flow of charge through a conductor, measured in amperes. Current flows when voltage pushes charge through a circuit against resistance, as described by Ohm's Law (I = V / R). In series circuits, current is the same everywhere; in parallel circuits, current splits across branches. Current is measured in series using an ammeter. Understanding current is essential for choosing the right components, calculating power consumption, and building safe circuits.