I have four different situation and i want to learn what kind of field (electric or magnetic) each produces and which produces electomagnetic waves?

1)dc current flow in a conductor

2)ac current flow in a conductor

3)q charge moving v velocity

4)q charge with a accelleration


closed as off-topic by Waffle's Crazy Peanut, user10851, Kyle Kanos, Brandon Enright, Abhimanyu Pallavi Sudhir Jan 2 '14 at 4:40

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Homework-like questions should ask about a specific physics concept and show some effort to work through the problem. We want our questions to be useful to the broader community, and to future users. See our meta site for more guidance on how to edit your question to make it better" – Waffle's Crazy Peanut, Community, Kyle Kanos, Brandon Enright, Abhimanyu Pallavi Sudhir
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    $\begingroup$ What do you want to know about electromagnetic waves? $\endgroup$ – NeutronStar Nov 3 '13 at 22:19

1) DC-current will result in a constant magnetic field, the right hand rule can be used here. See https://en.wikipedia.org/wiki/Magnetic_field#Magnetic_field_and_electric_currents for more information on that. An electromagnetic wave is not "produced" in the steady state case, as we ignore the activation operation.

2) An AC-current will result in a alternating magnetic field. An alternating magnetic field will cause an alternating electrical field and voila - you just made an antenna and will send electromagnetic waves. Anyhow, its a very bad antenna, but there are a lot of tricks to make them better.

3) Is the same case as 1)

4) An accelerated charge will always result in bremsstrahlung, see https://en.wikipedia.org/wiki/Bremsstrahlung for more information on that.

  • 1
    $\begingroup$ Afaik, For 3 the result is not quite the same as a dc current flowing in a conductor, because of the spatial and temporal dependence of the magnetic field. The way to obtain the result is to Lorentz transform the Coulomb field into a frame where $q$ is moving with velocity $v$. I don't think $E$ vanishes in this case, unlike a conductor in which $E$ is zero. $\endgroup$ – lionelbrits Nov 3 '13 at 22:59
  • $\begingroup$ Oh yes, you're right there. I overlooked the current is not continuous in this case. $\endgroup$ – Fips Nov 3 '13 at 23:15

Not the answer you're looking for? Browse other questions tagged or ask your own question.