By means of (5), (7) and (8), two equations emerge from I' II', which shall be simplified by putting:
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(9)
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Then it is given:
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I'a
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II'a
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III'a
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IV'a
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§ 3. The field in relatively resting media.
Let the only velocity of the system be , or which is the same, let it be in relative rest. Then , and the following equations – in all rigor – shall apply:
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I'b
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II'b
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IIIb
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IVb
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These equations have exactly the same form, as Maxwell's equations for a stationary system. Only by those equations, however, the field E, M and thus also the radiation relative to matter is determined, as far as certain quantities – "electric and magnetic quantities" – which are invariable according to those very equations, are required.[1] Thus for a while we postpone the consideration of these processes in which electromagnetic energy goes over into other forms of energy, especially mechanical work,[2] and then we can say:
- ↑ See in this respect, below p. 1409 f.
- ↑ See below § 5.