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mysearch
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What came first E or B?
This question is in the style of the chicken or egg, but I would be interested to hear any views as to whether the electric field is the primary source of energy and whether the magnetic field is essentially just a manifestation of this energy linked to a moving charge?
If we look at the units of energy [tex](kg.m^2/s^2)[/tex] and the electric field [tex](kg.m/Cs^2)[/tex], we have what seems to be a logical association, i.e. the electric field appears to align to force per charge or energy.metre per charge. If you apply the same logic to the magnetic field (B=kg/Cs), the association with energy is less clear until you add velocity by virtue of the relationship E/B=c. Of course, the relativity of a moving frame of reference also seems to indicate that any measure of a magnetic field is also relative.
So what is an EM wave and how do we measure the E and the M strength?
It would seem the Lorentz equation of force [tex]F=q(E+vB)[/tex] provides a suggestion that a test charge would be subject to a force if place in the path of an EM wave, but is E driving B or B driving E at all points in space based on Maxwell’s 3rd and 4th equation in vacuum, i.e.
[tex] -\frac {\partial B}{\partial t} = \nabla \times E [/tex]
[tex]\frac {1}{c^2} \frac {\partial E}{\partial t} = \nabla \times B [/tex]
I have swapped the ordering of these equations, as compared to post #10 in this thread, because I would have thought that the curl of E is the 'effect' resulting from the 'cause' being the rate of change of B with time, at least, in the specific case of a propagating EM wave. A similar argument applying to the 4th equation. However, if E and B are both in-phase in a propagating EM wave, is the rate of change of E with time still the primary physical force/energy at work here?
Would be interested in any clarifications of the points raised and I hope this question is in-line with the purpose of this thread.Thanks
This question is in the style of the chicken or egg, but I would be interested to hear any views as to whether the electric field is the primary source of energy and whether the magnetic field is essentially just a manifestation of this energy linked to a moving charge?
If we look at the units of energy [tex](kg.m^2/s^2)[/tex] and the electric field [tex](kg.m/Cs^2)[/tex], we have what seems to be a logical association, i.e. the electric field appears to align to force per charge or energy.metre per charge. If you apply the same logic to the magnetic field (B=kg/Cs), the association with energy is less clear until you add velocity by virtue of the relationship E/B=c. Of course, the relativity of a moving frame of reference also seems to indicate that any measure of a magnetic field is also relative.
So what is an EM wave and how do we measure the E and the M strength?
It would seem the Lorentz equation of force [tex]F=q(E+vB)[/tex] provides a suggestion that a test charge would be subject to a force if place in the path of an EM wave, but is E driving B or B driving E at all points in space based on Maxwell’s 3rd and 4th equation in vacuum, i.e.
[tex] -\frac {\partial B}{\partial t} = \nabla \times E [/tex]
[tex]\frac {1}{c^2} \frac {\partial E}{\partial t} = \nabla \times B [/tex]
I have swapped the ordering of these equations, as compared to post #10 in this thread, because I would have thought that the curl of E is the 'effect' resulting from the 'cause' being the rate of change of B with time, at least, in the specific case of a propagating EM wave. A similar argument applying to the 4th equation. However, if E and B are both in-phase in a propagating EM wave, is the rate of change of E with time still the primary physical force/energy at work here?
Would be interested in any clarifications of the points raised and I hope this question is in-line with the purpose of this thread.Thanks
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