What Are the Units of Electromagnetic Wave B?

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Homework Help Overview

The discussion revolves around determining the units of the magnetic field B in the context of electromagnetic waves, utilizing relationships involving angular frequency (ω), wave number (k), and electric field (E). Participants are exploring the derivation of units and the relationships between various physical quantities.

Discussion Character

  • Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to derive the units for B using the equation B = k / ω (Z x E) and discussing the implications of different variables. Questions arise regarding the correctness of unit conversions and the relationships between quantities like voltage and velocity.

Discussion Status

The discussion is active, with participants providing various unit derivations and questioning each other's reasoning. Some guidance is offered regarding the interpretation of symbols and units, but there is no explicit consensus on the final units of B.

Contextual Notes

There is mention of potential confusion between voltage (V) and velocity (v), indicating a need for clarity in notation. Additionally, participants note the complexity of the unit conversions involved, suggesting that some assumptions may need to be revisited.

dowjonez
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B = k / w ( Z x E)

Check this equation by deriving the units for B


w = omega
Z = z hat
 
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What have you done so far?
 
k = 2pi / lamdba
w = 2 pi V / lamba

So B = 1/V ( Z X E)

B = 1/ [ m / s ] ( Z X E )

[E] = [q] / [E0] [ R^2]

[E] = [C] / [C^2/ Nm^2] [ m^2] = [N / C]

B = [s / m] * ( Z x [N / C])
 
but = N / A * m
 
[C / s] = [A], so 1/[A] = [s / C]

[N] / [Am] = [N / m]*[1/A], right? so [N]/[Am] = [s/C]*[N/m], or [s/m]*[N/C]

I may have missed something, but I don't see a problem.

Also, be careful. V = voltage, v = velocity. It was hard to read your posts with some of those things in caps. This could have been easier if you noticed immediately that k/w = 1/v, which has units [s/m], and that E always has units [N/C]. Maybe you were expected to work it all out, but that's silly.
 
Last edited:

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