# Recent content by Keiner Nichts

1. ### Calculating the amplification of a transistor

Thanks a bunch!
2. ### Calculating the amplification of a transistor

Oh, thank you, with that, I have managed to correctly determine the amplification without the load, as being -Rc/(Re+re). Now, Rc seems to be tied in parallel with the load because they have the same voltage difference on them. I am wondering, if Rc's resistance would not be equal to the load's...
3. ### Calculating the amplification of a transistor

Homework Statement In the circuit shown below, I have to find the amplification for when the commutator which connects to the 4 kΩ resistance is open, respectively closed. We know the Beta factor to be 200, and the current through the base is negligible. The transistor is made of silicone...
4. ### Complex Numbers problem

Homework Statement If Z1+Z2+Z3=0 and Z1*Z2 + Z2*Z3 + Z3*Z1=0 and Z1, Z2, Z3 are all complex, what is the value of (|z1|+|z2|+|z3|)/(|z1*z2|+|z2*z3|+|z3*z1|) Homework Equations The Attempt at a Solution I tried to multiply the equations by the product of all conjugates and reach some...
5. ### Number of modes in Cubic Cavity

Thank you! As for the radiant energy, would mere multiplication with N give me the right answer? I see no reason why it should not, just making sure.
6. ### Number of modes in Cubic Cavity

Homework Statement Calculate the number of modes in a cubic cavity of length a=2.5 cm in the wavelength interval (λ1,λ2) where λ1=500 nm and λ2=501 nm. What's the total energy which radiates from the cavity if it's kept at a constant temperature of T=1500 K. Homework Equations I imagine these...
7. ### The Sun treated as a perfect Black Body

Well, for the temperature I got the Sun's temperature at the photosphere (or a very good approximation at least, I got the real value from Wikipedia), so I imagine the total intensity is good as well. Thank you a lot!
8. ### The Sun treated as a perfect Black Body

Oooh, ok, so it's only emitted from the surface. Now...if I were to consider the output as constant, it means that the given value in the beginning, let's call it P, would satisfy: P×4πr^2=P'×4πR^2 where P' is what I need to find. And then through Stefan Boltzmann I divide it by the constant and...
9. ### The Sun treated as a perfect Black Body

I know the given power is proportional to T^4 through the Stefan-Boltzmann law but I was not really taught the formula for how the incident power changes with r. I imagine it would be proportional to (1/r)^2? Also, temperature of the Sun would be proportional to either (1/R)^2 or (1/R)^3 for...
10. ### The Sun treated as a perfect Black Body

Homework Statement At lunch, the Sun's thermal energy incident on the surface of the Earth is 1.4 kW/m^2. Given the radius of the Sun, R, distance from Earth, r, and treating the Sun like a perfect black body, calculate the total intensity of its radiation and determine its temperature...
11. ### Electrostatic Energy in the Hydrogen Atom

Thank you. I think I might've reached a rather satisfactory result using the form in mks units. It seems alright dimensionally, at least.
12. ### Electrostatic Energy in the Hydrogen Atom

I reckon merely the electric field energy. Though, unfortunately, that is as clear as the question gets...For a superficial distribution I was able to simply assess the potential of interaction between the proton and the electron, and also the potential the electron generates when it interacts...
13. ### Electrostatic Energy in the Hydrogen Atom

Homework Statement We model the Hydrogen atom as a charge distribution in which the proton (a point charge) is surrounded by negative charge with the volume density of ρ = -ρ0 * exp (-2r/a0) where a0 is the Bohr radius. And ρ0 is a constant chosen such that the entire atomic distribution is...