Physics: Electricity and Magnetism Practice Flashcards

A collection of vocabulary-style flashcards covering the fundamental concepts of electrostatics, dielectrics, conductors, and DC circuits based on the lecture transcript.

Electric flux through an area $dS$

A physical quantity with a magnitude proportional to the number of electric induction lines passing through that area.

Electric field strength at a point

A physical quantity measured by the force of the electric field acting on a unit positive charge placed at that point.

Behavior of a dielectric crystal in an AC voltage

If an alternating voltage is applied to two opposite faces, the crystal will consecutively compress, expand, and vibrate at the frequency of the alternating voltage.

Bound charges (Linked charges)

Charges that appear on the two limiting surfaces of a dielectric block (opposite to the direction of the electric field vector) when placed in an external electric field.

Capacitor

A system consisting of two conductors in a state of total electrostatic induction.

Current in metals

The directed movement of electrons.

Conductor in electrostatic equilibrium

A conductor where the charged particles are in a stationary state, the electric field inside is zero ($E = 0$), and the entire conductor is an equipotential volume.

Electric field inside a dielectric

When a dielectric block is placed in an external electric field, the internal electric field decreases by $\frac{1}{\tan}$ times (or a factor of $\tan$) compared to the external field.

Property of electric field lines and equipotential surfaces

Electric field lines are always perpendicular to the equipotential surface.

Electromotive force (EMF) of a source

A quantity equal to the work done by non-electrostatic (external) forces in moving a unit positive charge once around a closed circuit of that source.

Vortex electric field (Induced electric field)

An electric field produced by a time-varying magnetic field, characterized by closed field lines and non-zero work when moving a charge along a closed path.

Electric potential at a point

A quantity equal to the work done by the electrostatic force in moving a unit positive charge from that point to infinity.

Secnhet dielectric (Ferroelectric)

A special dielectric that maintains polarization after the external field is removed, has a very high permittivity ($10^4$) depending on field strength, and loses these properties above the Curie temperature.

Work of electrostatic force

The work done moving a charge $q$ from point $M$ to $N$ depends only on the positions of the starting and ending points, not the shape of the path.

Electric field inside a metal sphere ($r < R$)

$$E = 0$$

Electric field outside a metal sphere ($r > R$)

$$E = \frac{1}{4 \times \text{pi} \times \text{epsilon}_0 \times \text{epsilon}} \times \frac{Q}{r^2}$$

Coulomb's Law (Vector form)

$$\mathbf{F} = \frac{1}{4 \times \text{pi} \times \text{epsilon}_0 \times \text{epsilon}} \times \frac{q \times q_0}{r^2} \times \frac{\mathbf{r}}{r}$$

Energy density of a uniform electric field ($w$)

$$w = \frac{\text{epsilon} \times \text{epsilon}_0 \times E^2}{2}$$

Current Density ($j$)

$j = \frac{dI}{dS_{\perp}}$, representing the current per unit area perpendicular to the flow.

Potential of a point charge $q$

$$V = \frac{1}{4 \times \text{pi} \times \text{epsilon}_0 \times \text{epsilon}} \times \frac{q}{r}$$

Energy of a capacitor ($W$)

$$W = \frac{C \times U^2}{2} = \frac{q \times U}{2} = \frac{q^2}{2 \times C}$$

Capacitance of a parallel plate capacitor ($C$)

$$C = \frac{\text{epsilon} \times \text{epsilon}_0 \times S}{d}$$

Electromotive force formula

$$\mathcal{E} = \frac{A_{ext}}{q}$$

Ohm's Law in differential form

$$\mathbf{j} = \text{sigma} \times \mathbf{E}$$

Capacitance of an isolated conductor

$$C = \frac{q}{V}$$

Electric field inside a uniformly charged dielectric sphere

The electric field $E$ inside the sphere increases linearly with the distance $r$ from the center to the outer surface.