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6 months ago in Electromagnetics By Pranav

Wait, there are two different permittivities of free space?

I keep seeing "permittivity of free space" and "relative permittivity of free space" and they have different values. Which one is right?

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By Babita Answered 2 months ago

They're not competing they're different things. ε? (about 8.854×10?¹² F/m) is an absolute physical constant. It tells you how much electric field the vacuum itself can support. Relative permittivity (ε?) is a ratio: it compares a material's permittivity to ε?. For free space, that ratio is exactly 1. So the "relative permittivity of free space" is just 1, by definition. Same vacuum, two different measurements.

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