What is Electric Current?

What is Electric Current actually ?

The name "current" indicates that Electric Current is a flow of something. Not a flow of current. A flow of electrons, ions or some other very tiny things or liquid like water? In Electronics it is a flow of electric charges. Charge is not a thing, but a property measurable and related with force (electrical force). Charges are said to be "carried" by electrons, ions or some other tiny things. In Electronics, however, current is more precisely defined as the quantity of charges passed through an area, or more generally through a point (any point in a volume, or area or line) per time. Or more generally by including of the changing quantity with time, it is a rate change of the quantity of charges which go through a point with time.

The following article (form physicsclassroom.com) explains Electric Current in a similar way.

http://www.physicsclassroom.com/class/circuits/u9l2c.cfm

Electric Current

If the two requirements of an electric circuit are met, then charge will flow through the external circuit. It is said that there is a current - a flow of charge. Using the word current in this context is to simply use it to say that something is happening in the wires - charge is moving. Yet current is a physical quantity that can be measured and expressed numerically. As a physical quantity, current is the rate at which charge flows past a point on a circuit. As depicted in the diagram below, the current in a circuit can be determined if the quantity of charge Q passing through a cross section of a wire in a time t can be measured. The current is simply the ratio of the quantity of charge and time.

http://www.physicsclassroom.com/class/circuits/u9l2c.cfm


The article says

As a physical quantity, current is the rate at which charge flows past a point on a circuit.

But it does not elaborate charge flows past a point and changes to the quantity of charge Q passing through a cross section of a wire in a time t by using a diagram. In terms of the rate, this seems the same thing, either past a point or through a cross section.

A small cross section can be regarded as a point? - Yes and No.

Yes - A limit of an area (volume and line as well) is a point.

No - A point is zero dimension while an area is two (2) dimensions.

Yes and No

When the quantity of charge Q passing through a cross section in a time t divided by the area, we can get an average of the quantity of charge Q passing through a cross section. And this average can be regarded as the charge Q passing through a point.
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