← Reference notes

Source and license: OpenStax, Paul Peter Urone, Roger Hinrichs et al., "College Physics" (1st edition), OpenStax, Rice University, openstax.org/details/books/college-physics. Licensed CC BY 4.0. This page is an AI-assisted summary by iinventedlight in its own words, not the textbook itself.

Summary

Electricity is the behaviour of electric charge. Charge pushed by a voltage flows as a current, resistance limits how much flows, and Ohm's law (V = IR) ties the three together. Power is the rate at which a circuit turns electrical energy into heat, light or motion (P = IV). Circuits combine resistors in series or parallel, and they run on direct current (one direction) or alternating current (back and forth, as in household mains).

Facts

• id: F1 claim: Charge comes in two kinds, positive and negative. Like charges repel and unlike charges attract. Total charge is conserved, and it comes in whole multiples of the electron's charge, about 1.60 x 10^-19 coulombs. where: https://openstax.org/books/college-physics/pages/18-1-static-electricity-and-charge-conservation-of-charge sources: [S1] license: CC BY 4.0
• id: F2 claim: Current is the rate at which charge flows past a point, I = charge / time. One ampere is one coulomb per second. By convention, current points the way positive charge would move, which is opposite to the electrons' motion in a metal wire. where: https://openstax.org/books/college-physics/pages/20-1-current sources: [S1] license: CC BY 4.0
• id: F3 claim: Voltage (potential difference) is the energy per unit charge between two points. One volt is one joule per coulomb. A battery or generator supplies the voltage that drives current around a circuit. where: https://openstax.org/books/college-physics/pages/19-1-electric-potential-energy-potential-difference sources: [S1] license: CC BY 4.0
• id: F4 claim: Resistance (in ohms) measures how strongly an object opposes current. It grows with the length of a conductor, shrinks as its cross-section gets larger, depends on the material's resistivity, and usually rises with temperature in metals. where: https://openstax.org/books/college-physics/pages/20-3-resistance-and-resistivity sources: [S1] license: CC BY 4.0
• id: F5 claim: "Ohm's law: for many materials current is proportional to voltage, V = IR. Doubling the voltage across a fixed resistor doubles the current. Materials that follow this are called ohmic. It is an empirical rule, not a universal law." where: https://openstax.org/books/college-physics/pages/20-2-ohms-law-resistance-and-simple-circuits sources: [S1] license: CC BY 4.0
• id: F6 claim: Electric power is P = IV, which for a resistor also equals I^2 R and V^2 / R. One watt is one joule per second. Utilities bill energy in kilowatt-hours, power multiplied by time (1 kWh = 3.6 million joules). where: https://openstax.org/books/college-physics/pages/20-4-electric-power-and-energy sources: [S1] license: CC BY 4.0
• id: F7 claim: "A circuit needs a closed path. In series, the same current passes through every part and resistances add: R = R1 + R2 + .... In parallel, every branch has the same voltage and the reciprocals add: 1/R = 1/R1 + 1/R2 + ..., so the total is lower than the smallest branch." where: https://openstax.org/books/college-physics/pages/21-1-resistors-in-series-and-parallel sources: [S1] license: CC BY 4.0
• id: F8 claim: Direct current (DC), as from a battery, flows one way at a steady voltage. Alternating current (AC) reverses direction periodically, 60 times per second in North America (50 Hz in much of the world). AC is quoted by rms values, such as 120 V, which give the same average power as that DC voltage would. where: https://openstax.org/books/college-physics/pages/20-5-alternating-current-versus-direct-current sources: [S1] license: CC BY 4.0
• id: F9 claim: Grids use AC largely because transformers can easily step its voltage up for transmission, which cuts current and so I^2 R losses in the lines, and then step it down for safe use in homes. where: https://openstax.org/books/college-physics/pages/20-5-alternating-current-versus-direct-current sources: [S1] license: CC BY 4.0

Licence

Text in this note: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), condensed by iinventedlight from OpenStax, Paul Peter Urone, Roger Hinrichs et al., "College Physics" (1st edition), https://openstax.org/details/books/college-physics, CC BY 4.0. Changes: facts restated and condensed; no text, figures or problems copied.

@misc{iil_note_kg5fc3pm,
  author = {{iinventedlight Library}},
  title = {{How electricity works (charge, current, voltage, resistance, Ohm's law, power, circuits, AC and DC)}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-10-23},
  url = {https://iinventedlight.com/library/reference/openstax/how-electricity-works/},
  note = {Permanent ID iil:note:kg5fc3pm. License: CC-BY-4.0. Summary of https://openstax.org/books/college-physics/pages/preface.},
}

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