Ch. 23 Glossary - College Physics 2e | OpenStax

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Glossary

back emf: the emf generated by a running motor, because it consists of a coil turning in a magnetic field; it opposes the voltage powering the motor

capacitive reactance: the opposition of a capacitor to a change in current; calculated by $X_{C} = \frac{1}{2π fC}$

characteristic time constant: denoted by $τ$ , of a particular series RL circuit is calculated by $τ = \frac{L}{R}$ , where $L$ is the inductance and $R$ is the resistance

eddy current: a current loop in a conductor caused by motional emf

electric generator: a device for converting mechanical work into electric energy; it induces an emf by rotating a coil in a magnetic field

electromagnetic induction: the process of inducing an emf (voltage) with a change in magnetic flux

emf induced in a generator coil: $emf = NAB ω sin ωt$ , where $A$ is the area of an $N$ -turn coil rotated at a constant angular velocity $ω$ in a uniform magnetic field $B$ , over a period of time $t$

energy stored in an inductor: self-explanatory; calculated by $E_{ind} = \frac{1}{2} {LI}^{2}$

Faraday’s law of induction: the means of calculating the emf in a coil due to changing magnetic flux, given by $emf = - N \frac{ΔΦ}{Δt}$

henry: the unit of inductance; $1 H = 1 Ω \cdot s$

impedance: the AC analogue to resistance in a DC circuit; it is the combined effect of resistance, inductive reactance, and capacitive reactance in the form $Z = \sqrt{R^{2} + (X_{L} - X_{C})^{2}}$

inductance: a property of a device describing how efficient it is at inducing emf in another device

induction: (magnetic induction) the creation of emfs and hence currents by magnetic fields

inductive reactance: the opposition of an inductor to a change in current; calculated by $X_{L} = 2π fL$

inductor: a device that exhibits significant self-inductance

Lenz’s law: the minus sign in Faraday’s law, signifying that the emf induced in a coil opposes the change in magnetic flux

magnetic damping: the drag produced by eddy currents

magnetic flux: the amount of magnetic field going through a particular area, calculated with $Φ = BA cos θ$ where $B$ is the magnetic field strength over an area $A$ at an angle $θ$ with the perpendicular to the area

mutual inductance: how effective a pair of devices are at inducing emfs in each other

peak emf: ${emf}_{0} = NAB ω$

phase angle: denoted by $ϕ$ , the amount by which the voltage and current are out of phase with each other in a circuit

power factor: the amount by which the power delivered in the circuit is less than the theoretical maximum of the circuit due to voltage and current being out of phase; calculated by $cos ϕ$

resonant frequency: the frequency at which the impedance in a circuit is at a minimum, and also the frequency at which the circuit would oscillate if not driven by a voltage source; calculated by $f_{0} = \frac{1}{2π \sqrt{LC}}$

self-inductance: how effective a device is at inducing emf in itself

shock hazard: the term for electrical hazards due to current passing through a human

step-down transformer: a transformer that decreases voltage

step-up transformer: a transformer that increases voltage

thermal hazard: the term for electrical hazards due to overheating

three-wire system: the wiring system used at present for safety reasons, with live, neutral, and ground wires

transformer: a device that transforms voltages from one value to another using induction

transformer equation: the equation showing that the ratio of the secondary to primary voltages in a transformer equals the ratio of the number of loops in their coils; $\frac{V_{s}}{V_{p}} = \frac{N_{s}}{N_{p}}$

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Authors: Paul Peter Urone, Roger Hinrichs
Publisher/website: OpenStax
Book title: College Physics 2e
Publication date: Jul 13, 2022
Location: Houston, Texas
Book URL: https://openstax.org/books/college-physics-2e/pages/1-introduction-to-science-and-the-realm-of-physics-physical-quantities-and-units
Section URL: https://openstax.org/books/college-physics-2e/pages/23-glossary

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