Electric Circuits Glossary

An instrument that measures electric current. Connected in series with the component; built with very low resistance.

A device that stores charge and energy in the electric field between two conductors (plates): $C = Q/V$. SI unit: farad (F).

The rate of flow of electric charge: $I = \Delta Q / \Delta t$. SI unit: ampere (A). Conventional current flows from high to low potential.

The voltage provided by a source (battery, generator) when no current flows. Symbol: $\varepsilon$. Represents the energy per unit charge supplied to the circuit.

The resistance within a battery or power source that causes the terminal voltage to be less than the EMF when current flows.

The sum of currents entering any node equals the sum leaving it. A consequence of conservation of charge.

The sum of voltage changes around any closed loop in a circuit equals zero. A consequence of conservation of energy.

The linear relationship between voltage, current, and resistance: $V = IR$. Valid for ohmic materials at constant temperature.

The rate of electrical energy conversion: $P = IV = I^2R = V^2/R$. SI unit: watt (W).

A circuit containing a resistor and capacitor. Exhibits exponential charging/discharging behavior with time constant $\tau = RC$.

The opposition to current flow: $R = V/I$. Depends on material resistivity, length, and cross-sectional area. SI unit: ohm ($\Omega$).

The work done per unit charge between two points in a circuit: $V = W/q$. SI unit: volt (V = J/C).

An instrument that measures potential difference (voltage). Connected in parallel across the component; built with very high resistance.