MEPX
Chapter 11 of 13All chapters
  1. 1What physics is
  2. 2Units and measurement
  3. 3Describing motion
  4. 4The laws of motion
  5. 5Forces
  6. 6Energy and work
  7. 7Momentum and collisions
  8. 8Waves
  9. 9Sound
  10. 10Light and optics
  11. 11Electricity and magnetism
  12. 12Heat and thermodynamics
  13. 13Modern physics

Chapter 11 of 13

Electricity and magnetism

Charge, current and the field between them.

The basic quantities

Current is the flow of charge in amperes, voltage is the push that drives it, and resistance opposes it. Ohm's law ties them together as voltage equals current times resistance.

  • Power in a circuit is voltage times current, in watts.
  • In series the current is shared; in parallel the voltage is.

The link to magnetism

A moving charge makes a magnetic field, and a changing magnetic field drives a current. Motors and generators are the same machine run in opposite directions.