Find the radius Rrigel of the star Rigel, the bright blue star in the constellation Orion that radiates energy at a rate of 2.7×
1 answer:
Answer:
r = 1.61 x 10^{11} m
Explanation:
energy radiated (H) = 2.7 x 10^31 W
surface temperature (T) = 11,000 k
assuming ε = 1 and taking σ = 5.67 x 10^{-8} W/m^{2}.K^{4}
we can find the radius of the star from the equation below
H = A x ε x σ x T^{4}
where area (A) = 4 x π x r^{2} (assuming it is a sphere)
therefore the equation becomes
H = 4 x π x r^{2} x ε x σ x T^{4}
2.7 x 10^31 = 4 x π x r^{2} x 1 x 5.67 x 10^{-8} x (11,000)^{4}
r =
r = 1.61 x 10^{11} m
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Answer:
Reactance
Explanation:
In an AC circuit, the capacitive reactance of a capacitor is given by:
where
f is the frequency of the AC current
C is the capacitance of the capacitor
The reactance of the capacitor tells somehow the "resistance" of the capacitor to the passage of current through it. In fact:
- When the frequency of the AC current is zero (this means, we are in regime of DC current), the reactance becomes infinite, and this is true because the capacitor does not let the current pass through it)
- When the frequency of the AC current tends to infinite, the reactance becomes zero, and this is true because in this case the current changes direction so fast that the capacitor has not enough time to "block" the current, so the current almost no feels the presence of the capacitor.