# Moving charge and magnetism

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1. Nov 20, 2014

### Dikshant

If an electric charge is moving with constant velocity,what does it create?? A constant magnetic field or 1 which is varying with time?? What if it accelerate?

2. Nov 20, 2014

### Vagn

Does a wire with a constant current through it create a magnetic field?

3. Nov 20, 2014

### Dikshant

Thanks for reply,but m already a bit confused and that's a different case.

4. Nov 20, 2014

### Dikshant

Yeah,a constant magnetic field

5. Nov 20, 2014

### ChrisVer

6. Nov 20, 2014

### Dikshant

And
And what happens when a varying electric field is working in an area??

7. Nov 20, 2014

### Staff: Mentor

The fields from a moving charge are given by the Lienard Wiechert potentials

http://en.wikipedia.org/wiki/Liénar...onding_values_of_electric_and_magnetic_fields

It doesn't have an explicit time dependence, but the input variables are functions of time so the result is also.

8. Nov 20, 2014

### Staff: Mentor

9. Nov 20, 2014

### ChrisVer

Yes you are right DaleSpam...
Indeed, I misinterpreted this...I also thought about that when I saw the $r$ in the equation, but then... I got confused with the $u=const$ case not generating electromagnetic radiation... but the EM radiation is something different (has to do with the Poynting vector as well)...

10. Nov 20, 2014

### Staff: Mentor

Yes that is correct. The fields generated by the Biot Savart law or the Lienard Wiechert potential for constant velocity do not generate "radiation". The fields stay localized to the charge. They change over time, as the charge moves, but their relationship to the charge doesn't change.

11. Nov 20, 2014

### Dikshant

Thank you all