2025-2026 Science Resource Guide: Electricity, Magnetism, and Electromagnetic Waves (Jordan High School)

A set of Question-and-Answer style flashcards covering core concepts from electricity, magnetism, and electromagnetic waves presented in the notes.

What is Coulomb’s law and what does it describe?

FE = k q1 q2 / r^2; describes the electric force between two point charges, an inverse-square law where like charges repel and opposite charges attract.

How is the electric field from a point charge expressed, and in what direction does it act?

E = k q / r^2; the field points away from a positive charge and toward a negative charge.

State Gauss’s law in its integral form.

ΦE = q_enclosed / ε0; the electric flux through a closed surface equals the enclosed charge divided by the permittivity ε0.

What is the electric field for an infinite sheet of charge?

E = σ / (2ε0); the field is constant with distance and points away from the sheet for positive σ.

What does electric potential difference (voltage) represent and how does it relate to work?

Voltage is the electric potential difference; moving a charge q across this difference changes its electric potential energy by qV (ΔU = qV).

State Ohm’s Law and what it relates.

I = V / R (or V = IR); relates current, voltage, and resistance in circuits.

How is electrical power related to voltage, current, and resistance?

P = IV; equivalently P = I^2R or P = V^2/R; power is the rate of energy transfer.

Define a capacitor and state its key properties.

A capacitor consists of two conductors separated by a dielectric; storage of charge with C = Q/V; energy stored is ½CV^2; dielectric increases capacitance; dielectric breakdown can occur (air ~3 MV/m).

What does Faraday’s law of induction state?

V = −N ΔΦB/Δt; a changing magnetic flux through a circuit induces an emf; Lenz’s law gives the negative sign.

State Ampere’s law for a long straight wire.

B(2πr) = μ0 I; the magnetic field wraps around the wire and falls with distance.

What is the magnetic force on a moving charge?

FB = q v × B; the force is perpendicular to both velocity and magnetic field; direction found with the right-hand rule.

Describe the magnetic field inside a long solenoid.

B = μ0 I (N/L); inside a long, tightly wrapped solenoid the field is nearly uniform.

How does a bar magnet create a magnetic field, and how can a compass respond?

Field lines exit the north pole and enter the south pole; a compass aligns with the local magnetic field.

Explain the right-hand rule for the magnetic force on a moving charge.

Point thumb in velocity, index finger in B, and the perpendicular direction of the resulting force is given by your palm/fingers (follow standard right-hand rule).

What is the magnetic field around a long straight wire as a function of distance?

B = μ0 I /(2πr); field strength decreases with distance from the wire.

What is the magnetic field inside a solenoid in Ampere’s law form?

B = μ0 I (N/L); field strength inside a solenoid depends on current and turns per length.

How do transformers relate voltages to turns in coils?

V1/V2 = N1/N2; higher turns give higher voltage; current adjusts inversely to conserve power (P ≈ IV).

What are Maxwell’s equations (in essence) that unite electricity and magnetism?

Gauss’s law for electricity; no magnetic monopoles (Gauss’s law for magnetism); Faraday’s law of induction; Ampere’s law with displacement current.

What is the significance of the speed of light c being a universal constant?

c ≈ 3×10^8 m/s and equals 1/√(ε0 μ0); the same for all observers, leading to relativity effects like time dilation and length contraction.

How are wavelength and frequency related for electromagnetic waves?

c = λf; longer wavelength means lower frequency; shorter wavelength means higher frequency.

What is polarization and how do polarizers work?

Polarization is the orientation of the electric field; polarizers pass only one orientation; unpolarized light becomes polarized, and crossed polarizers block most light.

Why can light travel through a vacuum while sound cannot?

Electromagnetic waves propagate as oscillating electric and magnetic fields and need no medium; sound requires a material medium to propagate.

Define conductors and insulators with respect to electricity.

Conductors allow free movement of charges (e.g., metals); insulators resist charge flow (e.g., plastic, rubber); Faraday cages use conductors to shield fields.

What is a Faraday cage?

A conducting enclosure that shields its interior from external electric fields by redistributing surface charges.

What is charge conservation in electricity?

Total electric charge is conserved; charge is transferred between objects but not created or destroyed.

Name the four fundamental forces and identify which governs electricity.

Gravity, strong nuclear, weak nuclear, and electromagnetic; electricity is governed by the electromagnetic force.

Give the approximate masses of the proton and the electron.

mp ≈ 1.67×10^−27 kg; me ≈ 9.11×10^−31 kg (electrons are far lighter than protons).

What is the elementary charge e and its approximate value?

The magnitude of charge on a proton or electron: e ≈ 1.60×10^−19 C (proton +e, electron −e).

What is the Lorentz factor and what does it imply about relativity?

γ = 1/√(1−v^2/c^2); leads to time dilation and length contraction; as v approaches c, γ increases without bound.

How do electric and magnetic fields transform under relativity?

Different observers may describe the same phenomenon as electric or magnetic fields depending on their frame; the electromagnetic force is the unified interaction.

What is a dielectric and how does it affect capacitor performance?

A dielectric is an insulating material between capacitor plates that becomes polarized; increases capacitance and can prevent breakdown up to a limit.

What is dielectric breakdown and its practical implication?

When the electric field exceeds a material’s dielectric strength (air ~3 MV/m), the insulator becomes conductive, causing a breakdown (sparks or lightning in large-scale events).

What is the energy form relationship in a moving charge across a potential difference in a circuit?

As a charge moves through a potential difference V, its kinetic energy can increase by qV (per the session's convention).

What is the speed of light in vacuum and how does it relate to energy waves?

c ≈ 3×10^8 m/s; EM waves propagate at this speed in vacuum; the speed emerges from ε0 and μ0 in Maxwell’s equations.