What is AC current (alternating current)

Alternating Current

We discussed in our previous topics that current is the flow electrical charges. The electrical charge was further defined as Electrons. There are two types of currents. i.e. Direct Current and alternating current. Both types of currents abbreviation are DC and AC respectively.However they are mostly said as AC current and DC current. Here we will discuss Alternating current(AC).

Definition of Alternating Current

An alternating current is the type of current in which the electric charge (Electrons) reverses its direction periodically. We further explain it as the current starts from zero and grows to a maximum limit. When it reaches maximum it starts decreasing towards zero. After reaching zero,it continues in the negative direction and continues to increase until it reaches a maximum point in the opposite direction.

After the maximum point, it follows the same procedure and returns to its original value, once it reaches its original position again it repeats the cycle and continue to repeat it for unlimited times. 

In simple words AC current is that current which is not fixed in both direction and magnitude.  It revers it direction 50 or 60 time per each single second.

AC current
AC current

Different Parameters of AC

The alternating current has different parameters we will discuss each in detail.

  1. Period of alternation current

The time interval between two consecutive crust or trough is called the period of alternating current. Another definition of the time period of alternating current is the value of time requires to attain the two successive levels.

  1. Frequency of Alternating current

The number of periods or cycles in one second is called frequency. Also, it is the number of back and forth oscillations of an AC voltage or current in one second. Different ranges of frequencies are used for different purposes and applications. Some of them are listed below.

  • The alternating current frequency of 50 to 60 hertz are low frequencies and used for domestic as well as commercial and industrial purposes.
  • Frequency range up to 100 Megahertz is used in television.
  • Frequency range above 100Megahertz is used microwave like radar etc.
  • Cellular mobiles use frequencies above 1 Gigahertz.


Advantages and Disadvantages of AC current

In this topic, we will only discuss the advantages and disadvantages of Alternating current. For a detailed definition of direct current and its properties please read our other topic “Direct Current”.

Advantages of Alternating current

  • The alternating current generation is easier than the Direct current.
  • For higher voltages, alternating current has less transmission losses.
  • We can convert alternating current to direct current using rectifiers if required.

Disadvantages of Alternating current

  • Alternating current or voltage cannot be used in electric traction,electroplating, or charging batteries. There is no way to store AC current.
  • Working on a higher alternating current is more dangerous than direct current.

AC current generation

To generate Alternating current we need AC generator. The generation may be 1 phase or 3 phases generator. Single phase ac current is mostly suitable for domestic loads where no much power needed and all motor are single phase induction motors. But when it come to industrial and loads where large three phase induction motors and 3 phase loads are used, then a 3 phase AC generator is used.

  Alternating current formula

As mentioned above AC power generation is divided in two. 1 and 3 phases system.

Current formula for single phase loads.

 I = P / (V * I * cos Φ)

While current formula for AC 3 phases loads.

 I = P / (√3 * V * I * cos Φ)

How to measure ac current using multimeter?

Multimeter is the instrument which is used in electrical voltage, resistance, current and some more measurements. To use it for alternating current calculation simply select alternating current and connect the device in series with the load.

A better way to measure current is to use current clamp-meter which need no series connection. just put the device core around the cable and take the reading.

connecting the multimeter in series

free android app to calculate AC current

Android apps for electricians are very useful. You can use any of electrical calculator apps. For me as an electrical engineer I use FAST ELECTRICAL CALCULATOR free app. the app has also paid version so you can use the free one and then if you need ads free version install the paid one.

Click the below image to install the free version. Don’t worry its 100% free!

fast electrical app