AC Current

In another section, current was defined as motion of the electrons caused by a difference in potential or voltage. In the several sections, a battery was the source of direct current. It should be noted for that case, electron motion was only in one direction. When electronic flow is in one direction,  by definition this is known as direct current (DC).

When the source of voltage alternates in a positive and negative direction, it causes the electrons to flow in two directions in a cyclical fashion. In other words the voltage source which could be a generator at the power company will cause the current or electron flow to go along your wiring  first in one direction and then in another direction in a cyclical fashion like 60 Hertz or 60 cycles per second. In this situation the power generator is the source and the electrical devices in your house are refered to as the load. Ref: Figures below.


Alternating Current (ac) Waveform

 The sinusoidal waveform below represents your house ac current whereupon ONE CYCLE is equal to 1/60 second along the TIME LINE. In other words, 60 cycles would take place every second. The Cycle Rate used to be called 60 cycles per second or 60 Hertz. Notice that the current changes direction from Plus to Minus during each cycle. The Frequency is also known as the Cycle Rate. (Frequency can take values from near zero to the GHz region, which is in the billions). A quick reminder 0 Hz is actually dc resulting in a straight-line waveform versus time.




It should be noted that the Lionel O gauge trains operate via an alternating current variable transformer power pack, with exception of those that are Digital Command and Control (DCC) compatible.

AC Current can be measured by putting an AC Current meter in series with the load or by using an AC Clamp-On meter which clamps to the external wiring of interest without interupting the circuit.

If you wish to acquire a better understanding of Electronics Theory, I suggest you go to  the following  link: Electronics