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Alternating Current (AC)

It's common sense electron can flow either forwards or backwards along a conductor. We learnt with DC that DC is when current flows only in one direction. alternating current is when current flows in both directions, first one direction and then the other, alternating between directions, often extremely quickly. This alternating current has quite a few benefits being, easier to generate, less transmission costs and easier to transform to different voltages, so it is quite widely used.

AC has these important properties
  • Voltage - Since the voltage (or 'pressure') is in one direction and the other it is not as easy to state as DC. There are peak and the voltage doesn't instantly swap from one to the other, it happens smoothly so there also many in between voltages. In fact most often it appears in a sin wave pattern like the diagram below. voltage for AC current is equal to the same amount of work a DC voltage is capable of doing. For a sine wave like our example below that is .707 * the peak power. For example household power is either 240V or 120V AC and comes in sine form, so it has peak of 338.4V or 169.2V.

    AC Sine Wave

  • Frequency - So we know that the current keeps changing directions, how often it does it is called the frequency. This record as the number of complete wave (or cycles) that pass a point per second record in HERTZ (Htz). For example your mains power at home is 60 or 50 Htz which means that it goes from 0 volt to a high peak to 0 to a low peak and back to 0 50 or 60 times in one second.

    AC Sine Wave frequency



Alternating Current

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Anonymous
172
Actually, looking at the diagram you might say that it's at about 4.1Hz. This is an important thing to consider.

In the electromagnetic world cycles do not represent transfer of energy but rather a change of state. If you were to increase this to 60Hz you would not see an increase in the energy, just the number of cycles. You might see an increase in the energy (voltage) dependent upon the length of the line the electricity was run through, however this would not be a direct product of the frequency rather the ability of your conductor to carry a DC charge (resistance).
MatMI
1
So in the diagram as stated above it means the cycle is 4Hz right?

What if i were to increase the number of cycles?
Would that mean that the energy current increases?
More energy?

thanks
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