Chapter 20 – Electric Circuits Vocabulary

A set of 50 vocabulary flashcards covering key terms and definitions from Chapter 20, Electric Circuits.

Electric circuit

A closed conducting path in which an energy source drives electric charges through energy-consuming devices.

Electromotive force (emf)

The maximum potential difference a source such as a battery can provide between its terminals.

Electric current (I)

The amount of charge that passes through a cross-section per unit time; I = Δq ⁄ Δt.

Coulomb (C)

The SI unit of electric charge; 1 _ equals the charge transported by 1 A in 1 s.

Ampere (A)

The SI unit of current, defined as one coulomb of charge per second.

Direct current (dc)

Current in which charges move in the same direction at all times.

Alternating current (ac)

Current in which charge flow reverses direction periodically.

Conventional current

The hypothetical flow of positive charges used to describe circuit behavior, opposite the motion of electrons.

Resistance (R)

The ratio of voltage across a material to the current through it; R = V ⁄ I.

Ohm’s Law

States that V ⁄ I is constant for many materials, giving V = IR; the constant is resistance.

Ohm (Ω)

The SI unit of resistance; 1 _ = 1 V ⁄ 1 A.

Resistor

A component or material that presents a specific resistance to current flow.

Resistivity (ρ)

A material property relating resistance to geometry: R = ρL ⁄ A.

Temperature coefficient of resistivity (α)

Parameter that describes how a material’s resistivity changes linearly with temperature.

Electric power (P)

The rate at which electrical energy is delivered or converted; P = IV.

Watt (W)

The SI unit of power; equals one joule per second.

Power relation for resistors

Alternate forms of power: P = I²R = V² ⁄ R for purely resistive elements.

Root-mean-square (rms) value

Effective dc equivalent of an ac quantity; Irms = Io ⁄ √2 and Vrms = Vo ⁄ √2.

Peak voltage (Vo)

The maximum (amplitude) value of an alternating voltage waveform.

Series circuit

A wiring arrangement in which the same current passes sequentially through each device.

Equivalent series resistance (RS)

The sum of individual resistances in series: RS = R1 + R2 + R3 + …

Parallel circuit

A wiring arrangement in which the same voltage is applied across each device.

Equivalent parallel resistance (RP)

The reciprocal sum of individual resistances: 1 ⁄ RP = 1 ⁄ R1 + 1 ⁄ R2 + …

Internal resistance (r)

The inherent resistance within a battery or generator that causes a voltage drop when current flows.

Terminal voltage

The actual voltage measured across a source’s terminals while delivering current: Vterminal = emf − Ir.

Kirchhoff’s junction rule

The sum of currents entering a junction equals the sum leaving; expresses charge conservation.

Kirchhoff’s loop rule

Around any closed circuit loop, the sum of potential rises equals the sum of potential drops; energy conservation.

Ammeter

Instrument inserted in series to measure current with minimal added resistance.

Voltmeter

Instrument connected across two points to measure voltage, designed with very high resistance.

Galvanometer

Sensitive coil-and-pointer device that deflects proportionally to small currents; basis for ammeters and voltmeters.

Shunt resistance

A low-value resistor placed parallel to a galvanometer to divert excess current and extend measurement range.

Capacitor

A device that stores electric charge and energy in an electric field between two conductors.

Capacitance (C)

A measure of a capacitor’s ability to store charge per unit voltage; C = q ⁄ V, SI unit farad (F).

Capacitors in parallel

Add like resistors in series: CP = C1 + C2 + C3 + …

Capacitors in series

Combine like resistors in parallel: 1 ⁄ CS = 1 ⁄ C1 + 1 ⁄ C2 + …

RC circuit

A circuit containing a resistor and capacitor that exhibits exponential charging or discharging behavior.

Time constant (τ)

Product of resistance and capacitance, τ = RC; time for charge or voltage to change by ~63%.

Capacitor charging

Process where capacitor voltage rises as q(t) = q0(1 − e^(−t/RC)).

Capacitor discharging

Process where stored charge decays as q(t) = q0 e^(−t/RC).

Electromotive source

Any device (battery, generator) that converts non-electrical energy into electrical energy providing emf.

Impedance plethysmography

Medical technique using resistance change in a limb to monitor blood flow.

Alternator

A generator in vehicles producing ac that is rectified to charge the battery and power systems.

Extension-cord heating hazard

Thin, long cords have higher resistance, causing extra voltage drop and heating when powering high-current devices like space heaters.

Three-way light bulb

Bulb with two filaments wired in parallel-series combinations to provide three illumination levels.

Battery energy delivery

Total energy supplied equals q·V; useful for estimating battery life in devices.

Power dissipated in a resistor

Energy per unit time converted to heat or light in a resistor; given by I²R or V²/R.

Circuit junction

A point where three or more conductors meet, distributing current according to Kirchhoff’s junction rule.

Circuit loop

Any closed conducting path used when applying Kirchhoff’s loop rule for potential changes.

Electrical grounding

Safety practice of connecting circuits to Earth to prevent dangerous potentials and reduce shock risk.

Touch-screen resistive matrix

Thin transparent conductive layers that form a coordinate resistor grid for position sensing in personal electronic devices.

Impedance (general)

AC analog of resistance representing total opposition (resistive + reactive) to current flow.