Differences

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--- un:radiation-resistance [2024/06/30 05:06] – asad
+++ un:radiation-resistance [2024/06/30 05:07] (current) – [Impedance of free space] asad
@@ Line 23: / Line 23: @@
 $$ R_0 = \frac{4\pi}{c} = \frac{1}{c\epsilon_0} = 377 \ \Omega $$
-because $\epsilon_0=1/(4\pi)$ has to be used while converting from Gaussian to SI units.
+because $\epsilon_0=1/(4\pi)$ has to be used while converting from Gaussian to SI units. The definition of impedance of free space has to be this because $P=V^2/R$ which entails $S=V^2/(Rl^2)$ because flux is power per unit area.
 A black hole has the same radiation resistance as free space because it is a perfect absorber. So a black hole totating in an external magnetic field can generate electricity with $V/I$ ratio of 377 $\Omega$ which might power the jets of a [[quasar]].