College Physics II — Electricity, Magnetism and Optics flashcards
10 of 79 cards free to study here · 14 topics · the whole deck is built into Willys
Algebra-based electricity, magnetism and light with worked numbers: Coulomb's law, fields, potential, capacitors, resistance, Kirchhoff's rules, magnetic forces, induction and transformers, AC circuits, EM waves, mirror and thin-lens sign conventions, wave optics and modern physics.
Learn deck · part of College Physics I/II (algebra-based) · written against: Standard two-semester algebra-based sequence; OpenStax College Physics 2e, consulted as a reference; no text copied. Updated 2026-10-10.
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How many electrons must be removed from a neutral object to give it a charge of +1.0 μC?n = q ÷ e = (1.0 × 10⁻⁶ C) ÷ (1.60 × 10⁻¹⁹ C) ≈ 6.2 × 10¹² electrons. Even a tiny everyday charge involves trillions of electrons.Charge & Coulomb's Law
Watch out: μC means 10⁻⁶ C and nC means 10⁻⁹ C — convert before using Coulomb's law. -
A proton sits in a uniform electric field of 2.0 × 10⁴ N/C. What is its acceleration, and how does that compare with g?a = eE ÷ m = (1.60 × 10⁻¹⁹)(2.0 × 10⁴) ÷ (1.67 × 10⁻²⁷) ≈ 1.9 × 10¹² m/s², about 2 × 10¹¹ times g.Electric Field
Why: that is why gravity on individual charged particles is almost always ignored in electric-field problems. -
What is the equivalent capacitance of a 3.0 μF and a 6.0 μF capacitor connected in series? In parallel?In series, 1/C = 1/3.0 + 1/6.0 gives 2.0 μF; in parallel the capacitances simply add to 9.0 μF.Capacitance
Watch out: the rules are the reverse of those for resistors, and a series combination is always smaller than its smallest capacitor. -
How many electrons pass a point in a wire each second when the current is 2.0 A?A current of 2.0 A means 2.0 C per second, so n = 2.0 ÷ (1.60 × 10⁻¹⁹) ≈ 1.2 × 10¹⁹ electrons per second.Current & Resistance
Why: with so many carriers, each one only needs to drift very slowly to carry a large current. -
An electron moves east through a magnetic field that points north. Which way is the magnetic force on it?For a positive charge, the right-hand rule for east × north gives up, so on the negative electron the force points straight down.Magnetism
Watch out: apply the right-hand rule as if the charge were positive, then reverse the answer for electrons. -
A transformer's primary has 500 turns on 120 V AC. How many secondary turns give 6.0 V, and how does the secondary current compare with the primary's?÷ = ÷ , so = 500 × 6.0 ÷ 120 = 25 turns. For an ideal transformer power in equals power out, so the secondary current is 20 times the primary current.Electromagnetic Induction
Watch out: a step-down transformer steps the current up; it never creates energy. -
What is the wavelength of the signal from an FM radio station broadcasting at 100 MHz?λ = c ÷ f = (3.00 × 10⁸ m/s) ÷ (1.00 × 10⁸ Hz) = 3.0 m.Electromagnetic Waves
Why: antennas work best when their size is a sizable fraction of the wavelength, which is why FM antennas are typically around a meter long (a quarter to a half wavelength). -
In the mirror equation 1/ + 1/ = 1/f, which signs go with concave and convex mirrors and with real and virtual images?f is positive for concave and negative for convex mirrors. is positive for a real image in front of the mirror and negative for a virtual image behind it, and a negative magnification m = −/ means inverted.Reflection & Mirrors
Watch out: the most common error is forgetting the minus sign on a convex mirror's focal length. -
A grating has 600 lines per millimeter. At what angle does the first-order maximum for 550 nm light appear?First find the spacing: d = 1 mm ÷ 600 ≈ 1.67 × 10⁻⁶ m. Then sin θ = λ/d = 0.33, so θ ≈ 19°.Wave Optics
Watch out: "lines per mm" is not d — take its reciprocal and convert to meters. -
What handy shortcut gives a photon's energy in electron-volts from its wavelength in nanometers, and what is the energy of 400 nm violet light?Since hc ≈ 1240 eV·nm, E (eV) ≈ 1240 ÷ λ (nm). A 400 nm photon carries 1240 ÷ 400 ≈ 3.1 eV.Modern Physics
Why: it skips the 10⁻³⁴ and 10⁻¹⁹ exponents and makes eV-level problems quick to check.
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Checked against:
- OpenStax College Physics 2e, consulted as a reference; no text copied.
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