Practical takeaway
DC keeps the same polarity; AC reverses direction periodically. Radios use both, often in the same piece of equipment.
Electricity & Electronics
AC & DC
See the difference between current that keeps one direction and current that reverses direction.
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Technician exam focus
Know the basic difference between alternating current and direct current, and recognize common sources and uses of each.
Two ways current can behave
DC: direct current
The polarity stays the same and current keeps the same overall direction.
AC: alternating current
The polarity reverses repeatedly, so the current reverses direction too.
Why hams care
Radios may run from DC supplies while RF signals are alternating electrical signals at much higher frequencies.
STEMulation
Switch between DC and AC
DC stays on one side of zero.