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Voltage vs. Current: What's the Difference?

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Read the comparison below, or explore it visually. Create a visual lesson comparing voltage and current using available credits or plan allowance.

Voltage is the electrical push, or energy per unit charge, between two points, while current is the rate at which electric charge actually flows past a point. Voltage is measured in volts (joules per coulomb) and current in amperes (coulombs per second); Ohm's law links them, since the current through a conductor equals the voltage across it divided by its resistance.

At a glance

VoltageCurrent
What it isEnergy given to each unit of chargeAmount of charge flowing per second
SI unitVolt (V) = joule per coulombAmpere (A) = coulomb per second
Measuring deviceVoltmeter, connected in parallelAmmeter, connected in series
Water-pipe analogyWater pressure differenceFlow rate of water
Exists without flow?Yes, across an unconnected batteryNo, needs a closed circuit

Which should you use?

Voltage

Voltage is the figure to check when matching a supply to a device, such as a phone charger rated for 230 V Indian mains or a remote that needs two 1.5 V cells.

Current

Current is the figure to check when sizing wires and fuses, because a heater drawing about 9 A needs thicker wiring and a higher-rated fuse than a 0.5 A LED lamp.

Frequently asked questions

Which is more dangerous, voltage or current?
Current flowing through the body causes harm, but voltage determines how much current can be pushed through the skin's resistance. A high voltage can drive a dangerous current, which is why mains wiring should only be handled by a qualified electrician.
Can there be voltage without current?
Yes. A battery on a shelf has a voltage across its terminals, but no current flows until a closed circuit connects them. Current needs both a voltage to push the charge and a complete conducting path for it to travel along.
How are voltage and current related?
Ohm's law states V = I × R: for a conductor at constant temperature, current rises in proportion to voltage. Doubling the voltage across a fixed resistance doubles the current, while doubling the resistance at the same voltage halves it.