13.Short tips for voltage and current

Voltage, (v):

Voltage is a measure of the energy carried by the charge.
Strictly: voltage is the "energy per unit charge".

The proper name for voltage is potential difference or p.d. for short, but this term is rarely used in electronics.

Voltage is supplied by the battery (or power supply).

Voltage is used up in components, but not in wires. We say voltage across a component.

Voltage is measured in volts, V.

Voltage is measured with a voltmeter, connected in parallel.

The symbol V is used for voltage in equations.

Current (I):

Current is the rate of flow of charge.

Current is not used up, what flows into a component must flow out.

We say current through a component.

Current is measured in amps (amperes), A.

Current is measured with an ammeter, connected in series.

The symbol I is used for current in equations.