2 Q's: EM radiation produced by positive charge

Click For Summary

Discussion Overview

The discussion revolves around two questions regarding electromagnetic (EM) radiation produced by an oscillating electric charge. Participants explore the implications of graphs representing electric and magnetic fields, the appearance of these graphs based on the charge's oscillation, and the relationship between the motion of the charge and the resulting fields.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants assert that the graphs provide information about the electric and magnetic fields, questioning what specific aspects are unclear.
  • There is a suggestion that the appearance of the graph depends on the nature of the oscillation, with sinusoidal oscillation leading to sinusoidal graphs.
  • One participant expresses confusion regarding the interpretation of the EM graph, particularly whether it represents direction or magnitude.
  • Another participant clarifies that the EM graph shows both magnitude and direction, with electric and magnetic field curves being perpendicular to each other.
  • There is a discussion about how the electric field behaves in relation to the charge's motion, with some participants emphasizing that the electric field moves along rather than up and down.
  • One participant acknowledges difficulty in understanding the relationship between the charge's motion and the electric field, suggesting a need for further research.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and confusion regarding the graphs and the relationship between the charge's motion and the resulting fields. There is no consensus on the interpretation of certain aspects of the graphs or the implications of the oscillation.

Contextual Notes

Some participants reference external resources for clarification, indicating that the discussion may depend on specific definitions and interpretations of the graphs. There are unresolved questions about the relationship between the electric field and the charge's motion.

abro
Messages
20
Reaction score
0
I have 2 questions about EM radiation produced by an occilating electric charge.
Q1: With graphs of electromagnetic fields, you can see that it contains an electric and magnetic component. What does these mean or give information about?
Q2: By occilating the charge, you will get such a graph. How will it look like?

I have tried drawing, doing research on the Poyting vector and I keep finding that the magnetic field will be in the opposite direction on the graph, in the case of the positive charge. And I sure know how to find the direction of a magnetic field...
 

Attachments

  • Some questions.png
    Some questions.png
    28.9 KB · Views: 556
Physics news on Phys.org
Q1. these graphs give information about the electric and magnetic fields... what don't you understand?
Q2. How the graph looks depends on how you oscillate the charge ... if you oscilate the charge sinusoidally, for example, you will get sinusoidal graphs.
See: http://www.cco.caltech.edu/~phys1/java/phys1/MovingCharge/MovingCharge.html

You are given a position-time graph for the charge; what does the acceleration-time graph look like?
 
Simon Bridge said:
Q1. these graphs give information about the electric and magnetic fields... what don't you understand?
Q2. How the graph looks depends on how you oscillate the charge ... if you oscilate the charge sinusoidally, for example, you will get sinusoidal graphs.
See: http://www.cco.caltech.edu/~phys1/java/phys1/MovingCharge/MovingCharge.html

You are given a position-time graph for the charge; what does the acceleration-time graph look like?

With the picture I attached, you can find the EM graph aswell. What I don't understand about that graph is wether it's the direction or magnitude of the the field. I have tried understanding what the graph of a charge moving sinusoidally look like, but it's inconsistent with for example the Poyting vector.
 
The example EM graph on what you supplied shows both the magnitude (the line) and the direction (the arrow). That is why the E and the B curves are drawn perpendicular to each other.

The graph of the sinusoidally moving charge is given to you in thr same picture - top right - as y vs t. This is a position-time graph. There is nothing wrong with it.
 
Simon Bridge said:
The example EM graph on what you supplied shows both the magnitude (the line) and the direction (the arrow). That is why the E and the B curves are drawn perpendicular to each other.

The graph of the sinusoidally moving charge is given to you in thr same picture - top right - as y vs t. This is a position-time graph. There is nothing wrong with it.

So when the charge moves up, the electric field moves up?
The magnetic field move in a circle when it moves up, but it's in the other direction when moving up, that's the problem I run into.
 
The electric field moves along, not up and down.
The magnitude may increase and decrease with time, and it may change direction.

How is the electric field related to the motion of the charge?
Don't guess - if you don;t know, look it up. I gave you a link even.
 
Simon Bridge said:
The electric field moves along, not up and down.
The magnitude may increase and decrease with time, and it may change direction.

How is the electric field related to the motion of the charge?
Don't guess - if you don;t know, look it up. I gave you a link even.

Took me some time to get the applet running, but now I can grasp it. Thanks!
 

Similar threads

Undergrad Does a time varying magnetic field in vacuum produce electric field or not?
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad How can magnetic fields contain energy?
  • · Replies 17 ·
Replies
17
Views
3K
Graduate Are all EM waves produced by accelerating charges?
  • · Replies 29 ·
Replies
29
Views
10K
Undergrad How Do Time-Varying Currents in Conductors Generate EM Fields and Waves?
  • · Replies 3 ·
Replies
3
Views
2K
High School Thought Experiment on Charge Carriers and Electrical Conduction
  • · Replies 3 ·
Replies
3
Views
980
Undergrad Charge movement relative to magnetic field frame dependence/invariance
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Magnetic field when the area of the plates of a capacitor increases
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Can nested solenoids trap particles?
  • · Replies 12 ·
Replies
12
Views
1K
High School Electric Field Direction: Are We Assuming a Universal Positive Frame?
  • · Replies 20 ·
Replies
20
Views
3K
Undergrad How to obtain Hamiltonian in a magnetic field from EM field?
  • · Replies 6 ·
Replies
6
Views
2K