Hi Joe,

Electrical current seems to have a direction and magnitude. So is it a vector quantity?

## Is current a vector?

### Re: Is current a vector?

The normal convention for a current that stays in a quasi-one dimensional conductor such as a wire is

• treat the current as a scalar, which is conserved along the wire

• treat the local direction of the wire as a vector.

So, for instance, we write the magnetic force on a small section of wire

Because of conservation of current, and the fact that the wire is usually bent, it's convenient to have

When we are not in a 1D conductor, then we need to use current density, to allow for variation in space. So in that case, the current density (symbol

Joe

• treat the current as a scalar, which is conserved along the wire

• treat the local direction of the wire as a vector.

So, for instance, we write the magnetic force on a small section of wire

**carrying current***dl**i*as**=***dF**i***X***dl**B*Because of conservation of current, and the fact that the wire is usually bent, it's convenient to have

*i*as a scalar, so it can have the same value around the circuit.When we are not in a 1D conductor, then we need to use current density, to allow for variation in space. So in that case, the current density (symbol

**) is a vector.***J*Joe