# Oscillating Dipole: E & B Fields Near Source

• jc09
In summary, the conversation discussed the effects of E and B fields far from a source and the differences in the near field. It was mentioned that the equations for the near field are more complicated, but can still be solved for an oscillating dipole. The focus on the far field was because it is simpler and provides a good idea of polarization and power distribution. It was suggested to refer to Jackson's E&M text for further understanding. It was also mentioned that for a dipole in the near zone, the distances to the charges must be considered separately, making it a more complicated problem. The difference between the "radiation zone" and the "near zone" was also discussed.

#### jc09

Was studying in class the effects of the E and B fields far from the source and what they looked like, but we failed to discover what happens near the source...Is this because there is no difference or did we just not cover the material

In the near field, the equations are more complicated. For the oscillating dipole, you can still solve them, however. I'm guessing you focused on the far fields because they are simpler and give you a good idea of the distribution of polarization and power radiated.

Ok so they are different how would you go about solving them for the near field then?

I don't know how much you already know and what sort of explanation would help. But to describe it would take too long here, anyway. If you have a copy of Jackson's E&M text, look in chapters 8 and 9.

ok I'll give that book a look thanks

If the distance from the test point to one of the charges is r1 and the other charge is r2, when distance separating the dipole charges is significantly less than than r1 and r2, then the charges can be handled as if they were both an equal distance, r, from the test point (i.e. r=r1=r2). This simplifies the calculation. As you consider test points closer to the dipole, the difference in their distances, |r2-r1|, becomes a factor and you can no longer use the single distance r.

My apologies - you're looking at dipole radiation.

So when we calculated the fields far from the source the distance from each was the same cause the difference between the two was so small but close to the source the distances have to be taken as separate values so more complicated problem yeah?

Yeah - at least that's so for analyzing the static dipole. For the dynamic case, (if you have JD Jacksons text on Classical Electrodynamics, see pg 411) he describes the difference between the "radation zone" (relatively far from the dipole) and the "near zone" where the E field predominates. The field in near zone behaves more like the static case.

## What is an oscillating dipole?

An oscillating dipole refers to a system of two opposite charges that are separated by a distance and are undergoing periodic motion. This motion creates an oscillating electric field and a corresponding oscillating magnetic field.

## What is the significance of an oscillating dipole?

An oscillating dipole is significant because it is a fundamental concept in electromagnetism and plays a role in various physical phenomena such as radiation, resonance, and energy transfer.

## How are the E and B fields near the source of an oscillating dipole?

The E and B fields near the source of an oscillating dipole are perpendicular to each other and to the direction of propagation. The electric field is strongest along the direction of motion of the charges, while the magnetic field is strongest at right angles to the direction of motion.

## What factors affect the strength of the E and B fields near the source of an oscillating dipole?

The strength of the E and B fields near the source of an oscillating dipole is affected by the frequency and amplitude of the oscillation, as well as the distance from the source. The strength of the fields decreases with increasing distance from the source.

## Can an oscillating dipole produce electromagnetic waves?

Yes, an oscillating dipole can produce electromagnetic waves. As the charges in the dipole oscillate, they create changing electric and magnetic fields that propagate through space as electromagnetic waves. This is the basis of radio communication and other wireless technologies.