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  1. K

    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...
  2. K

    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...
  3. K

    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...
  4. K

    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...
  5. K

    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...
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