# Current and its speed

1. Sep 3, 2011

### kapil phyreak

i read somwhere that current travels with speed of light.....is it true?

2. Sep 3, 2011

### Bloodthunder

Electrical current travels at speed of light.
Water currents and air currents do not.

3. Sep 3, 2011

### Staff: Mentor

Define "current speed".

When you switch the light on, electromagnetic wave in the wire travels at the speed of light, but electrons drift speed is in the range of mm/s (or something in this range).

4. Sep 3, 2011

### Pengwuino

This is NOT true. Current does not travel at the speed of light.

@Borek: The e/m fields propagate at the speed of light, but isn't the speed of a "signal" dependent on how fast the electrons/protons move to propagate the electric field along a wire?

5. Sep 3, 2011

### Staff: Mentor

I always thought electric field propagates just like e/m filed - at the speed of light, is it in this regard in any way different from e/m field?

6. Sep 3, 2011

### HallsofIvy

Well, the "electric field" is part of the "electro-magnetic field"- but it isn't the field that propogates, it is waves in the electromagnetic field that propogate at the speed of light. In fact, light is waves in the electromagnetic field.

7. Sep 3, 2011

### Pengwuino

The way I'm imagining it is a neutral atom having an electric field applied. The field proceeds to displace the electrons so that some sort of multipole moment is formed which creates a field to do the same to the next atom and so on. In my mind, if this is true, the formation of the moments takes take to occur. I'm really not sure how it actually works though.