Electric Current Vocabulary

Flashcards for Electric Current Vocabulary

Electric Current

Charges in motion, occurring naturally like lightning or steadily in devices such as a torch or cell-driven clock.

Current (I)

The net amount of charge flowing across an area in the forward direction per unit time; I = q/t.

Current at Time t

The limit of the ratio of net charge flowing across a conductor's cross-section to the time interval as the time interval approaches zero; I(t) = lim(Δt→0) ΔQ/Δt.

Ampere

The SI unit of current, defined through magnetic effects of currents.

Conductors

Materials with electrons that are practically free to move within the bulk, allowing electric currents when an electric field is applied.

Ohm’s Law

A law stating that the potential difference (V) between the ends of a conductor is proportional to the current (I) flowing through it: V = RI.

Resistance (R)

The constant of proportionality (R) in Ohm's Law, representing the opposition to the flow of current in a conductor.

Ohm (Ω)

The SI unit of resistance, denoted by the symbol Ω.

Resistivity (ρ)

A property of a material that determines its resistance, independent of the conductor's dimensions; appears in the equation R = ρl/A.

Current Density (j)

Current per unit area, taken normal to the current flow; j = I/A.

Conductivity (σ)

The measure of a material's ability to conduct electric current; σ = 1/ρ.

Relaxation Time (τ)

The average time between successive collisions of electrons in a conductor.

Drift Velocity (vd)

The average velocity of electrons in a conductor due to an electric field.

Mobility (μ)

The magnitude of the drift velocity per unit electric field; μ = |vd|/E.

Semiconductors

Materials with resistivities characteristically decreasing with a rise in temperature, lying between conductors and insulators.

Temperature Coefficient of Resistivity (α)

The fractional increase in resistivity per unit increase in temperature; appears in the equation ρT = ρ0[1 + α(T – T0)].

Power (P)

The energy dissipated per unit time in a conductor; P = IV.

Electromotive Force (EMF) (ε)

The potential difference between the positive and negative electrodes of a cell in an open circuit (when no current is flowing).

Internal Resistance (r)

The resistance within a cell due to the electrolyte.

Kirchhoff’s Rules

Rules for analyzing electric circuits: (a) Junction rule: the sum of currents entering a junction equals the sum of currents leaving it; (b) Loop rule: the algebraic sum of changes in potential around any closed loop is zero.

Wheatstone Bridge

A bridge circuit with four resistors used to measure an unknown resistance by balancing the bridge.