Sections

Glossary
# Glossary

- ammeter
- an instrument that measures current

- analog meter
- a measuring instrument that gives a readout in the form of a needle movement over a marked gauge

- bridge device
- a device that forms a bridge between two branches of a circuit; some bridge devices are used to make null measurements in circuits

- capacitance
- the maximum amount of electric potential energy that can be stored (or separated) for a given electric potential

- capacitor
- an electrical component used to store energy by separating electric charge on two opposing plates

- conservation laws
- require that energy and charge be conserved in a system

- current
- the flow of charge through an electric circuit past a given point of measurement

- current sensitivity
- the maximum current that a galvanometer can read

- digital meter
- a measuring instrument that gives a readout in a digital form

- electromotive force (emf)
- the potential difference of a source of electricity when no current is flowing; measured in volts

- full-scale deflection
- the maximum deflection of a galvanometer needle, also known as current sensitivity; a galvanometer with a full-scale deflection of $\text{50 \mu A}$ has a maximum deflection of its needle when $\text{50 \mu A}$ flows through it

- galvanometer
- an analog measuring device, denoted by G, that measures current flow using a needle deflection caused by a magnetic field force acting on a current-carrying wire

- internal resistance
- the amount of resistance within the voltage source

- Joule’s law
- the relationship between potential electrical power, voltage, and resistance in an electrical circuit, given by ${P}_{e}=\text{IV}$

- junction rule
- Kirchhoff’s first rule, which applies the conservation of charge to a junction; current is the flow of charge; thus, whatever charge flows into the junction must flow out; the rule can be stated as ${I}_{1}={I}_{2}+{I}_{3}$

- Kirchhoff’s rules
- a set of two rules, based on conservation of charge and energy, governing current and changes in potential in an electric circuit

- loop rule
- Kirchhoff’s second rule, which states that in a closed loop, whatever energy is supplied by emf must be transferred into other forms by devices in the loop since there are no other ways in which energy can be transferred into or out of the circuit; thus, the emf equals the sum of the $\text{IR}$ (voltage) drops in the loop and can be stated as $\text{emf}=\text{Ir}+{\text{IR}}_{1}+{\text{IR}}_{2}$

- null measurements
- methods of measuring current and voltage more accurately by balancing the circuit so that no current flows through the measurement device

- ohmmeter
- an instrument that applies a voltage to a resistance, measures the current, calculates the resistance using Ohm’s law, and provides a readout of this calculated resistance

- Ohm’s law
- the relationship between current, voltage, and resistance within an electrical circuit; $V=\text{IR}$

- parallel
- the wiring of resistors or other components in an electrical circuit such that each component receives an equal voltage from the power source; often pictured in a ladder-shaped diagram, with each component on a rung of the ladder

- potential difference
- the difference in electric potential between two points in an electric circuit, measured in volts

- potentiometer
- a null measurement device for measuring potentials (voltages)

- RC circuit
- a circuit that contains both a resistor and a capacitor

- resistance
- causing a loss of electrical power in a circuit

- resistor
- a component that provides resistance to the current flowing through an electrical circuit

- series
- a sequence of resistors or other components wired into a circuit one after the other

- shunt resistance
- a small resistance $R$ placed in parallel with a galvanometer G to produce an ammeter; the larger the current to be measured, the smaller $R$ must be; most of the current flowing through the meter is shunted through $R$ to protect the galvanometer

- terminal voltage
- the voltage measured across the terminals of a source of potential difference

- voltage
- the electrical potential energy per unit charge; electric pressure created by a power source, such as a battery

- voltage drop
- the loss of electrical power as a current travels through a resistor, wire, or other component

- voltmeter
- an instrument that measures voltage

- Wheatstone bridge
- a null measurement device for calculating resistance by balancing potential drops in a circuit