Alternating Current (AC)

Alternating Current (AC)

DC versus AC

Remember in Chapter 18, we learned direct current (DC). Direct current means a current that is flowing in only one direction, that is from positive terminal to the negative terminal of the battery in the circuit. Battery is one of the examples of DC source, while AC generator is the source of AC.

The meaning of the word 'alternate' is something occurs by turns; first one and then the other. Knowing that alternating current (AC) means the direction of a current always changing its turns. The proper definition of AC is a current that repeatedly reverses its direction. Alternating current is not only changing its direction, but it also changes its value. It does not have any similar values. This can be seen clearly from the GRAPH 2 below, in which you can also compare it with that of DC.

GRAPH: AC VERSUS DC

When it comes to calculation, we don't have any problem in writing down the value of DC because it is always constant. i.e. if it starts with 5A , then it will end with 5A. Meanwhile, for AC, we might have problems in choosing which value to be put in V=IR equation for example, as we don't have any fix value for the current. We cannot choose average current Iave as it is zero!!You can understand this through the positive and negative sides of GRAPH 2. It keeps cancelling each other. Scientist then came out with the concept of root mean square current Irms which hence enable us to calculate V= IrmsR .

Thank you,
Mdm Ummi Atiah KMPk

~ May it Benefits You ➽💕

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