Charge carries electrical effects.
Electrons carry negative charge. In metal conductors, some electrons can move through the material. Electric current describes a net movement of charge, not how much energy a device has stored.
A source such as a battery establishes a voltage difference. When a suitable complete path is connected, charge can flow and energy can be transferred to a load.
Voltage, current and resistance.
Voltage is energy per unit charge between two points, measured in volts (V). Current is the rate of charge flow past a point, measured in amperes (A). Resistance, in ohms (Ω), describes opposition to current.
These quantities are connected but not interchangeable. A voltage can exist across an open switch even though no current flows through that gap.
A first worked example.
For an ohmic resistor, V = I × R. Rearranging gives I = V ÷ R, so 12 ÷ 6 = 2 A.
Keeping the voltage at 12 V but increasing the resistance to 12 Ω reduces current to 1 A. This is a simple resistor model, not a complete description of an AC motor.
Connect the terms to a lift.
A report might describe a supply voltage, motor current or a resistive connection. Each refers to a different property. Knowing the difference helps you ask what was observed without jumping to a diagnosis.
The next lesson follows the path that current takes through a circuit.
A closer look
Conventional current is described as flowing from positive to negative through the external circuit. Electrons in metal drift in the opposite direction. Circuit calculations normally use conventional current.
Check your understanding
Does a voltage difference always mean current is flowing?
Reveal the explanation
No. There can be voltage across a gap in an open circuit while no current flows through that gap.