Signal from dipole detcted at loop in free space

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Homework Help Overview

The discussion revolves around the detection of a signal generated by a Hertzian dipole in free space, specifically focusing on the magnetic field detected at a wire loop. The problem involves understanding the relationship between the detected magnetic field and Maxwell's equations, particularly in the context of plane wave solutions.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the meaning of the expression B=iB0 exp[i(kz-wt)]ex and its relation to wave propagation. There are attempts to connect this to the Euler relation between exponential and trigonometric functions. Questions arise about the implications of an imaginary component in the wave representation and its physical significance.

Discussion Status

Participants are actively engaging with the mathematical concepts and hints provided. Some express uncertainty about their understanding and the implications of the hints. There is a recognition of the need to clarify the role of the imaginary unit in wave equations, but no consensus has been reached on the interpretations or solutions.

Contextual Notes

Participants mention constraints such as time limitations and the challenge of working through complex concepts independently. There is a clear emphasis on adhering to forum rules regarding the provision of hints rather than complete solutions.

Roodles01
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Homework Statement


A Hertzian dipole at origin generates a signal in empty space which is detected at a wire loop with position vector;
r=(50m)ez

Homework Equations


Signal is detected by changing magnetic field;
B(t)=B0 sin(2∏ft)ex
Show it is consistent with the Maxwell's solution to a plane wave
B=iB0 exp[i(kz-wt)]ex

The Attempt at a Solution


Hmmm! I'm not getting far enough manipulating Maxwell's equations to provide an answer. Could someone give a little help, please?
 
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Roodles01 said:

Homework Statement


A Hertzian dipole at origin generates a signal in empty space which is detected at a wire loop with position vector;
r=(50m)ez



Homework Equations


Signal is detected by changing magnetic field;
B(t)=B0 sin(2∏ft)ex
Show it is consistent with the Maxwell's solution to a plane wave
B=iB0 exp[i(kz-wt)]ex


The Attempt at a Solution


Hmmm! I'm not getting far enough manipulating Maxwell's equations to provide an answer. Could someone give a little help, please?

A few hints only; you need to grab the bull by the horns yourself:

1. what is really meant by B=iB0 exp[i(kz-wt)]ex?

2. know the complex Euler relation betw. exponent and sine/cos?

3. Keep in mind that, at the receiving antenna, time is defined as t = 0, which is delayed from that of the transmitting antenna, so there will be a phase lag between transmitter and receiver.

This is mostly math.
 
Thank you.
1. I think that B=iB0 exp[i(kz-wt)]ex is the propagation of the signal/wave in the x direction

2. Euler relation betw. exponent and sine/cos
e^ix = cos x + i sin x (circular wave [e^ix] split into 2 planes . . . . . .

3. I realize I may be doing things the wrong way, but doing things by yourself when you have no time & tired is sooo hard to follow the right path . . . .
I'm trying.
 
Roodles01 said:
Thank you.
1. I think that B=iB0 exp[i(kz-wt)]ex is the propagation of the signal/wave in the x direction
How can a signal be imaginary?
2. Euler relation betw. exponent and sine/cos
e^ix = cos x + i sin x (circular wave [e^ix] split into 2 planes . . . . . .
No circulraly polarized wave here. This hint means little until you figure out hint #1.

3. I realize I may be doing things the wrong way, but doing things by yourself when you have no time & tired is sooo hard to follow the right path . . . .
I'm trying.

I understand, but we are strictly prohibited from doing more than giving you hints and telling you if your approach is correct or not.
 
. . . . . "what is really meant by B=iB0 exp[i(kz-wt)]ex?"

This is a solution to the wave equation - a combination of sin(kz-wt) & cos(kz-wt).

"The electric field of a sinusoidal plane wave that travels in the direction of the
propagation vector k and is polarized transverse to that direction" . . . . is represented by this equation.

However, for this I have the general solution
E(r; t) = E0 sin (k.r - wt).
This is similar to the equation I have stated at the beginning, however I'm not sure where the "i" in front of Bo comes from.

I really do appreciate the hints. I'm not moaning, honest!
 
Last edited:
Roodles01 said:
. . . . . "what is really meant by B=iB0 exp[i(kz-wt)]ex?"

This is a solution to the wave equation - a combination of sin(kz-wt) & cos(kz-wt).

"The electric field of a sinusoidal plane wave that travels in the direction of the
propagation vector k and is polarized transverse to that direction" . . . . is represented by this equation.

However, for this I have the general solution
E(r; t) = E0 sin (k.r - wt).
This is similar to the equation I have stated at the beginning, however I'm not sure where the "i" in front of Bo comes from.

I really do appreciate the hints. I'm not moaning, honest!

No offense taken, mate! :-)

But you didn't answer my question: how can an electric wave be imaginary? If you answer that question correctly you will see why the "i" is needed ahead of the expression for the transmitted wave.
 

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