is current a scalar or a vector?

Answer 1

Hey there Shehzaad,

If you want to know if something is a vector, ask yourself if the quantity (eg. current) follows vector algebra i.e. does the quantity follow cross product, dot product, etc.

Quantities like Temperature and Current though seemingly have sign/direction aren't vectors as they dont follow the vector laws :)

Answer 2

If you are dealing with a current in an electric circuit then most of the time you only need to know the magnitude of the charge flow (and whether it is positive or negative). The current is confined to the conductor and the magnitude is sufficient for working out things like voltages and power.

However, a current is *flow* of charge and has both a direction and a magnitude, and is definitely a VECTOR quantity.

In general life, current can be thought of a scalar just as velocity (vector) boils down to speed (scalar) for most purposes.

The vector nature of current becomes critical when you start to consider the magnetic fields produced by a current, or the forces that a current in subjected to when it flows in a magnetic field.

If I is the current vector
B is the magnetic field vector,

then F, the force experienced per unit length by the current is the vector cross-product:

F = I x B

Answer 3

It's a vector, but as indicated elsewhere, most of the time we can ignore that. Think what the word "current" connotes. It's flow, like the flow of a river. And flow has both magnitude and direction.

For example, the river current is flowing 10 knots downstream to the south. A swimmer who can swim 2 knots want to swim from the east bank to the west bank directly on the other side. What direction must the swimmer swim relative to the river flow to do that? This is clearly a problem in vectors addition.

A current of coulomb charges (aka amperes) also has direction as well as the magnitude (number of coulombs flowing). The answer that gave F = I X B as the force vector from the flow of current I and magnetic flux B shows one of the times when the direction of the current I must be taken into account. F, the result, is a vector that points outward and perpendicular (normal to) the plane defined by the vectors I and B. Most of the time, especially for ordinary EE or physics, the direction of an electrical current is not germane.

Answer 4

It depends on the context. If you are talking about how much electric current flows through a resistor in a circuit (say when you're finding the power dissipated) then you aren't concerned with the direction the current is going and you would call the current a scalar.

But when you are calculating the magnetic field due to the current in a wire of a certain shape, then direction matters and you could call the current a vector.

Most of the time we talk about a current density J spread over a cross sectional area that is indeed a vector quantity.

Answer 5

A vector in general (beyond classical mechanics) is a quantity or entity that has more than one component of measure, and a single component has little or no meaning. For example, your street address is a vector: the number of your house has no significance without the street, city, state and zip code. A state vector in orbital mechanics has three components of position, 3 of acceleration, and the time at which these values existed.

In the case of current (I assume you refer to electrical current), if it is flowing in a wire, you know the direction. However, if it is flowing unconfined to a wire (like in a metalic solid, a liquid or plasma), then direction becomes important. Also, a related measure is found in alternating current: phase. In fact electrical engineers use the term "phasor" to describe both magnitude and phase relationship to some reference.

Answer 6

Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.
It doesn't matter what direction the current is flowing or even if it is changing directions (as in AC). It is a scalar.

Answer 7

Electric current has both magnitude and direction. It is a vector.