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  1. U

    PN Junction at Equilibrium

    Consider a PN junction doped with say phosphorous on the N side, and Boron on the P side. Initially, there is an opportunity for the electrons just below the N conduction band to drop to the lower available energy states just above the P valence band. This leaves the N side positively charged...
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    I Phase Speed of Wave in non-relativistic Doppler Shift Derivation

    Consider the situation where an observer at rest on the ground measures the frequency of a siren which is moving away from the observer at speed ##v_{Ex}##. Let ##v_w## be the speed of the sound wave. Let ##\lambda_0##, ##f_0##, ##\lambda_D##, and ##f_D## be the wavelengths and frequencies...
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    Generalized Lorentz Transformation

    Summary: The problem is to generalize the Lorentz transformation to two dimensions. Relevant Equations Lorentz Transformation along the positive x-axis: $$ \begin{pmatrix} \bar{x^0} \\ \bar{x^1} \\ \bar{x^2} \\ \bar{x^3} \\ \end{pmatrix} = \begin{pmatrix} \gamma & -\gamma \beta & 0 & 0 \\...
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    The Angular Momentum of an Electric and Magnetic Charge

    Relevant Equations: Angular momentum density stored in an electromagnetic field: $$\vec{l}_{em} = \epsilon_0[\vec{r} \times (\vec{E} \times \vec{B})]$$ Electric field of an electric charge: $$\frac{q_e}{4\pi\epsilon_0}\frac{r - r'}{|r - r'|^3}$$ Magnetic field of a magnetic charge...
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    Current induced from a changing magnetic field

    This question is motivated by Problem 7.12 in Griffiths Electrodynamics book. I have not included it in the homework section, because I have already solved it correctly. However, I question whether my solution which agrees with the solution's manual is correct. Relevant Equations: $$\Phi =...
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    A simple Proper Time Calculation

    Homework Statement Suppose a spaceship starts from rest from a space station floating in deep space and accelerates at a rate of |a| relative to the space station for 1.0 Ms. It then decelerates for the same amount of time at the same constant rate |a| to arrive at rest at another space station...
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    Tension on a string attached to two objects

    Homework Statement A person would like to pull a car out of a ditch. This person ties one end of a chain to the car's bumper and wraps the other end around a tree so that the chain is taut. The person then pulls on the chain perpendicular to its length. If the distance between the car and tree...
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    A simple static equilibrium problem

    Homework Statement Suppose we have a folding ladder, so that when its legs are spread it makes an isosceles triangle. Suppose it has a support that runs parallel to the ground. There is a bucket of paint that rests on top of the ladder, and the mass of the ladder is negligible. Data: The legs...
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    Temperature change of Water after dropping a ball into it

    Homework Statement Suppose we drop a lead ball of mass M into water of mass m from a height h and allow everything to settle down. What is the temperature change of the water? Assume that the container is well insulated. Homework Equations Potential Energy = mgh dU = mcdT where dU is the...
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    A basic conservation of energy question

    The question asks: Uranium nuclei are unstable and decay by emitting a helium nucleus, which contains two protons and two neutrons. Suppose the original nucleus has 92 protons and 146 neutrons before it emits the helium nucleus, and that the helium nucleus has an knknown speed as it departs from...
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