Electric charges can flow past a point over time {current, electricity}| {electric current}. Flowing charge has one-tenth light speed.
Current I per area A {current density}| equals conductivity K times electric field E: I/A = K*E. Current I equals current density j times cross-sectional area A: I = (I/A) * A = j*A.
Current tends to stay on conducting-material surface {skin effect}, because electrons repel each other.
Charge flow can alternate directions over time {alternating current}| (AC). Alternating voltages cause electrons to oscillate. Commercial alternating current oscillates at 60 Hz in USA and 50 Hz in most other countries.
comparison
Direct current has less power loss and more average power than alternating current.
voltage
In alternating-current circuits, average or effective voltage equals maximum voltage divided by square root of two. In alternating-current circuits, average or effective current equals maximum current divided by square root of two.
transformer
Transformers change alternating-current voltage.
Charge flow can be in one direction only {direct current}| (DC). Direct current has less power loss and more average power than alternating current. Adding voltage sources alters direct-current voltage.
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Date Modified: 2022.0225