MEPX
Chapter 7 of 10All chapters
  1. 1Charge and current
  2. 2Voltage
  3. 3Resistance and Ohm law
  4. 4Series and parallel
  5. 5Power and energy
  6. 6Components
  7. 7AC and DC
  8. 8Electrical safety
  9. 9Reading a circuit diagram
  10. 10Everyday electricity

Chapter 7 of 10

AC and DC

Two ways to deliver power.

The difference

Direct current flows one way, as from a battery. Alternating current reverses many times a second, which is how mains electricity is delivered.

  • Transformers change AC voltage efficiently and do nothing for DC.
  • Most electronics run on DC, which is what a power adapter converts to.

Why AC won

Transmission losses depend on current, so power is sent at very high voltage and stepped down near homes. That transformation is only easy with AC.