PHY 2054 Exam 3 Clear & Concise Review

Vocabulary flashcards covering core physics concepts, formulas, and laws for PHY 2054 Exam 3 (Chapters 21-24).

Magnetic Flux ($\Phi$)

A measure of the magnetic field passing through a loop area, given by $\Phi = BA\cos(\theta)$, where $B$ is field strength, $A$ is exposed area, and $\theta$ is the angle to the normal line perpendicular to the loop.

Faraday's Law of Induction

The law stating that a changing magnetic flux induces a voltage, given by $|\varepsilon| = N\left|\frac{\Delta\Phi}{\Delta t}\right|$, where faster flux change or more loop turns ($N$) produces greater voltage.

Lenz's Law

The principle that induced current opposes the change in magnetic flux: a counterclockwise current produces a field out of the page to oppose decreasing out-of-page flux (or entering into-page flux), whereas a clockwise current produces a field into the page.

Motional EMF

The induced voltage generated across a perpendicular moving conducting bar, calculated as $\varepsilon = BLv$, resulting in loop current $I = \frac{\varepsilon}{R}$, where $L$ is length, $v$ is speed, and $R$ is resistance.

Transformer

A device using changing flux between two coils to step voltage up or down according to $\frac{V_s}{V_p} = \frac{N_s}{N_p}$ and $V_p I_p = V_s I_s$, requiring changing AC current rather than steady DC.

Inductor

A coil that acts like electrical inertia by resisting sudden changes in current, producing a self-induced voltage $\varepsilon_L = -L\frac{\Delta I}{\Delta t}$ and storing magnetic energy $U_L = \frac{1}{2}LI^2$.

Air-Core Solenoid Inductance

The self-inductance of a coil given by $L = \frac{\mu_0 N^2 A}{\ell}$, where doubling turns quadruples inductance, doubling area doubles inductance, and doubling length with fixed turns halves inductance.

RL Circuit Time Constant ($\tau$)

The time constant $\tau = \frac{L}{R}$ characterizing the rate of current change in an RL circuit, where current reaches $63\%$ of its final value during growth and falls to $37\%$ of its initial value during decay after one $\tau$.

LC Circuit

An ideal circuit with no resistance where energy oscillates between the electric field of a capacitor and the magnetic field of an inductor at natural frequency $f = \frac{1}{2\pi\sqrt{LC}}$.

Root-Mean-Square (RMS)

The effective value of alternating voltage or current that yields equivalent resistor heating, calculated as $V_{\text{rms}} = \frac{V_{\text{max}}}{\sqrt{2}}$ and $I_{\text{rms}} = \frac{I_{\text{max}}}{\sqrt{2}}$.

Inductive Reactance ($X_L$)

The opposition of an inductor to AC current, measured in ohms ($\Omega$) as $X_L = 2\pi f L$, which increases directly with frequency.

Capacitive Reactance ($X_C$)

The opposition of a capacitor to AC current, measured in ohms ($\Omega$) as $X_C = \frac{1}{2\pi f C}$, which decreases as frequency increases.

ELI the ICE man

A phase-relationship mnemonic indicating that in an inductive circuit ($L$), voltage ($E$) leads current ($I$) by $90^\circ$, while in a capacitive circuit ($C$), current ($I$) leads voltage ($E$) by $90^\circ$.

Impedance ($Z$)

The total opposition of an RLC circuit to AC current flow, given by $Z = \sqrt{R^2 + (X_L - X_C)^2}$, relating RMS voltage and current via $I_{\text{rms}} = \frac{V_{\text{rms}}}{Z}$.

Power Factor

The cosine of the phase angle between voltage and current, defined as $\cos(\phi) = \frac{R}{Z}$, used to determine average power dissipation $P_{\text{avg}} = I_{\text{rms}}^2 R$.

Series Resonance

The condition occurring at resonant frequency $f_0 = \frac{1}{2\pi\sqrt{LC}}$ where inductive and capacitive reactances cancel ($X_L = X_C$), resulting in minimum impedance ($Z = R$) and maximum current.

Electromagnetic Wave

A traveling disturbance of mutually perpendicular, in-phase electric and magnetic fields that propagates through vacuum without any medium at speed $c = 3.00 \times 10^8\,\text{m/s}$, with peak amplitudes related by $E_{\text{max}} = c B_{\text{max}}$.

EM Wave Travel Direction

The propagation direction determined by the vector cross product of the fields, $\mathbf{E} \times \mathbf{B}$, in that specific order.

Radiation Pressure

The mechanical pressure exerted by electromagnetic radiation at normal incidence, equal to $p_{\text{absorbed}} = \frac{I}{c}$ for a fully absorbing surface and $p_{\text{reflected}} = \frac{2I}{c}$ for a perfect reflector.

Electromagnetic Spectrum

The ordered sequence of electromagnetic waves from lowest to highest frequency (longest to shortest wavelength): Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma.

Index of Refraction ($n$)

The ratio of the speed of light in vacuum to the speed of light in a material, given by $n = \frac{c}{v}$, where a larger index indicates slower light propagation.

Snell's Law

The law describing refraction across a boundary between two media: $n_1\sin(\theta_1) = n_2\sin(\theta_2)$, where angles are measured relative to the surface normal.

Total Internal Reflection

The phenomenon where light traveling from a higher index medium to a lower index medium is entirely reflected back into the first medium when the angle of incidence exceeds the critical angle.

Critical Angle ($\theta_c$)

The incident angle defined by $\sin(\theta_c) = \frac{n_{\text{low}}}{n_{\text{high}}}$, above which all light reflects internally and at which transmitted light runs along the boundary.

Real Image

An optical image formed where actual light rays converge, which can be captured on a screen and corresponds to an inverted orientation and positive image distance ($d_i > 0$) for single optical elements.

Virtual Image

An optical image formed where backward extensions of diverging light rays intersect, which cannot be projected onto a screen and corresponds to an upright orientation and negative image distance ($d_i < 0$).

Thin Lens and Mirror Equation

The equation $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$ relating focal length ($f$), object distance ($d_o$), and image distance ($d_i$).

Magnification ($m$)

The ratio given by $m = -\frac{d_i}{d_o}$, where a positive sign indicates an upright image, a negative sign indicates an inverted image, and the absolute magnitude indicates relative image size.

Spherical Mirror Focal Length

The distance from the mirror surface to its focal point, given by $f = \frac{R_{\text{curvature}}}{2}$, where concave mirrors have a positive focal length and convex mirrors have a negative focal length.