why electric current is a scaler quantity?

Answer 1

Good question Anshuls, A scalar quantity is the one that does not depend on the direction of the physical quantity, right? And the current does depend upon the direction it is flowing in the wire, isn't it?

But, that's a very superficial definition of the term "scalar quantity" or so to speak. A scalar quantity is the one which depends on magnitude only, specified completely by a single number alongwith the proper unit. So, although the current can be negative or positive depending on from which direction it is flowing, its value does not change if you bend the wire or change the wire's orientation.

You can add currents just like any other scalar quantity without giving the angle between the wires any consideration. If you have a wire A which has 2 Amperes of current flowing in it, and you connect it you a wire B which had 1 Amp of current flowing, and draw out another wire C from their junction, you will always get 3 (2+1) Amperes of current in the wire C no matter what is the direction of the wire and irrespective of the angle between the wires.

Now, if you had current flowing AWAY FROM THE JUNCTION in wire B, you could just have marked it as (-)1 amp instead of 1 ampere and you'd have gotten [(-)1 + 2] = 1 Ampere of current in wire C.

To sum up, as the rules for combining amperes are the rules of ordinary algebra, and they can be added, subtracted, multiplied and divided just as the ordinary numbers; they are units of a scalar quantity i.e. current.