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  1. C

    Energy of Capacitor in RC Circuit

    The instantaneous power delivered to a component is given by I * V where the I is the current through the component, and V is the voltage across the component. Note that the current through the resistor and capacitor are the same, because of Kirchoff's current law: I(t) = \frac{dQ(t)}{dt} =...
  2. C

    Prove x^3 - y^3 = (x - y)(x^2 +xy + y^2)

    Here is a method that doesn't involve manipulating the right hand side, which is more I think of what we're looking for: Artificially create a factor (x - y) and add canceling terms at the end: x^3 - y^3 = (x - y)( x^2 ) + ( x - y )( y^2 ) + x^2 * y - y^2 * x With the final two terms...
  3. C

    Quick QM Question

    Note that b_{n} = <\varphi_{n}|\Psi(x)> Can be a complex number. Does a complex probably mean anything? Hint hint...
  4. C

    Changing values of R in a RLC series circuit

    It seems like your set up is correct. What is the expression you get for \frac{| Z_1 |}{| Z_2 |} ? Though it doesn't seem like you need the info I wrote up below, it might be worth checking out: Your expression for the magnitude of the impedance of the circuit is correct, but is more...
  5. C

    Quick QM Question

    One important point you're missing is that \psi can be any linear combination of the energy eigenfunctions \phi_n. Try the problem armed with the knowledge that: \Psi(x,t) = \Sigma_n \phi_n(x,t) I would be glad to answer any further questions, but this seemed to be the major stumbling block.
  6. C

    Relativistic De Broglie wavelength

    The easy equations to use here are p = h / lambda and E^2 = ( p * c )^2 + ( m c^2 )^2 you're pretty much done at that point