Electricity Basics and Circuits 9

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Electricity

The presence and flow of electric charge

Electric current

The flow of electrons through a conductor

Electrons

Negatively charged subatomic particles found in atoms

Protons

Positively charged subatomic particles found in the nucleus of atoms

Neutrons

Subatomic particles with no charge found in the nucleus of atoms

Static electricity

Electric charges that are unable to move, also called electrostatic charges

Ion

An atom that gains or loses electrons and becomes charged

Like charges

Repel each other

Unlike charges

Attract each other

Charged objects

Attract neutral objects

Conductor

Material that allows electric charge (usually electrons) to flow through it easily

Insulator

Material that resists the flow of electric charge and does not allow electrons to flow easily

Semiconductor

Material with some electrical conductivity, but not as much as conductors; conductivity can be modified by doping

Electric current

The amount of charge that passes a point in a conductor each second; measured in amperes (A)

Ampere (A)

The unit of electric current

Milliampere (mA)

One thousandth of an ampere (1 mA = 0.001 A)

Electric insulator

Material that does not have free electrons and resists electric current (e.g., rubber, glass, plastic, air)

Voltage

Measure of how much energy is gained or lost by electrons as they move through a circuit; measured in volts (V)

Potential difference

The difference in electric potential between two points in a circuit; another term for voltage

Resistance

Opposition to the flow of electrons; measured in ohms (Ω)

Ohm (Ω)

The unit for electrical resistance

Resistor

A device that has electrical resistance and is used in a circuit for protection, operation, or current control

Ammeter

An instrument used to measure electric current; connected in series in a circuit

Voltmeter

An instrument used to measure voltage (potential difference) between two points in a circuit; connected in parallel

Series circuit

A circuit where components are arranged one after the other in succession

Parallel circuit

A circuit where components are arranged side by side, extending in the same direction

Direct current (DC)

Electric current flowing in one direction only; voltage remains constant

Alternating current (AC)

Electric current that periodically reverses direction; voltage varies with time

Transformer

A device that transfers alternating electric energy from one circuit to another

Efficiency

A measure of how much work or energy is conserved in a process

Diode

An electrical component that allows the flow of current in only one direction

Load

A device that converts electrical energy into another form of energy

Fuse

A safety device in a circuit that melts if current gets too high, breaking the circuit

Switch

A device that opens or closes a circuit to control the flow of electrons

Charging by contact

When a charged object touches a neutral object, causing electrons to move and leaving the neutral object charged

Friction

The process of rubbing two materials together, causing electrons to transfer and create static electricity

Grounding

Connecting a charged object to the ground to balance its charge by transferring electrons

Voltage drop

The amount of energy used by a component in a circuit; difference in potential across the component

Conventional current

The flow of positive charge from the positive terminal to the negative terminal of a power source

Electron current

The flow of electrons from the negative terminal to the positive terminal of a power source

Factors affecting resistance

Length of conductor (longer = more resistance), thickness (thinner = more resistance), material type, temperature (hotter = more resistance)

Van de Graaff generator

A device that generates high voltages by accumulating electric charge on a metal dome using a moving belt

Battery

A source of electrons; separates charge using chemical reactions to provide electrical energy in a circuit

Cell

A single unit that produces electricity by chemical means; multiple cells make a battery

Power supply

A device that provides electrical energy to a circuit

Globe

A light bulb used as a load in a circuit to convert electrical energy to light