Chapters 10–11: Electric Circuits, Current & Resistance

Vocabulary flashcards covering key terms from lecture notes on electric circuits, current, resistance, and related measurement instruments.

Electric Circuit

A complete, closed path through which electric current can flow.

Battery

An electric source that supplies electricity by converting chemical energy into electrical energy.

Generator

A device that supplies electricity by converting mechanical energy into electrical energy.

Electric Appliance

Any device that uses electricity to perform work, e.g., a bulb or electric motor.

Switch

A control device used to open or close an electric circuit.

Conducting Wire

A metal conductor that connects components in a circuit and provides a path for current.

Electric Current

The movement of electrons in a fixed direction; symbol I, measured in amperes (A).

Direction of Current

Conventional current flows from the positive terminal to the negative terminal, opposite to electron flow.

Closed Circuit

A circuit in which all components are connected and the switch is closed, allowing current to flow.

Open Circuit

A circuit with a break (open switch or frayed wire) that prevents current flow.

Short Circuit

A fault where the two terminals of a source are connected directly with no load in between.

Circuit Diagram

A schematic representation of an electric circuit using standard symbols.

Circuit Symbol

A standardized pictorial representation of a circuit component used in diagrams.

Series Circuit

A circuit where components are connected end-to-end; the same current flows through each part.

Parallel Circuit

A circuit where components are connected across common points, providing multiple current paths.

Branch Point

A junction in a parallel circuit where the current splits into different paths.

Primary Road

The section of a circuit from the source terminals to the first branch point.

By-trail

A branch circuit between branch points in a parallel connection.

Ammeter

An instrument connected in series to measure electric current; symbol A.

Voltmeter

An instrument connected in parallel to measure potential difference (voltage); symbol V.

Ampere (A)

The SI unit of electric current; 1 A = 1000 mA.

Milliampere (mA)

One-thousandth of an ampere; 1 mA = 1000 μA.

Microampere (μA)

One-millionth of an ampere.

Magnitude of Current

The numerical value (quantity) of electric current flowing in a circuit.

Conductor

Material that transmits electricity easily due to the presence of free electrons (e.g., metals).

Insulator

Material that does not transmit electricity because it lacks free-moving charges (e.g., rubber).

Semiconductor

Material whose conductivity lies between that of conductors and insulators; e.g., silicon, germanium.

Resistance

The property of a conductor that opposes current flow; symbol R, measured in ohms (Ω).

Ohm (Ω)

The SI unit of electrical resistance.

Fixed Resistor

A resistor with a set resistance value that cannot be adjusted.

Carbon Film Resistor

A fixed resistor made by depositing carbon film on a substrate.

Metal Film Resistor

A fixed resistor constructed with a thin metal film for stable resistance.

Wire-wound Resistor

A resistor made by winding resistive wire around an insulating core.

Metal Oxide Film Resistor

A resistor that uses a metal-oxide coating for high stability and heat resistance.

Rheostat

A variable resistor used to adjust circuit resistance and control current.

Sliding Rheostat

A rheostat whose resistance is varied by sliding a contact along a coil of wire.

Knob-turning Rheostat

A rheostat adjusted by rotating a knob to change resistance.

Factor: Length

Resistance increases with the conductor’s length.

Factor: Cross-Sectional Area

Resistance decreases as the cross-sectional area of the conductor increases.

Factor: Temperature

For most conductors, resistance increases with temperature.

Superconductivity

The phenomenon where a material’s resistance drops to zero below a critical temperature.

Transition Temperature

The temperature at which a material becomes superconducting.

Superconductor

A material that exhibits zero electrical resistance below its transition temperature.

Ohm’s Law

States that current (I) is directly proportional to voltage (V) and inversely proportional to resistance (R); I = V ⁄ R.

V = IR

A rearranged form of Ohm’s Law to calculate voltage across a resistor.

R = V ⁄ I

A rearranged form of Ohm’s Law to calculate resistance from voltage and current.

Free Electron

An electron in a metal that is not bound to an atom and can move freely, enabling conduction.

Variable Resistor Symbol

The circuit symbol representing a rheostat or adjustable resistor.

Double-Range Ammeter

An ammeter that offers two selectable measurement ranges for different current levels.