# Tagged Questions

Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.

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### Parallel combination of cells

In this circuit suppose that $E_1 >E_2$. This means that the positive terminal of $E_1$ will have a greater potential than the positive terminal of $E_2$. Then current should flow from the ...
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### Swirl velocity from circulation - Vortex

I have a vector field in cartesian coordinate $(x,y)$ with coordinate origin at vortex core. For calculating the swirl velocity $v_\theta$ I followed below steps, Step 1: Find the circle coordinates ...
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### Acceleration of a pulley system

The figure above shows a pulley system consisting of 3 masses ($m_1$, $m_2$ and $m_3$), a homogeneous wheel (radius R, mass M) and 2 massless pulleyes which are connected by a massless rope. Mass $m_1$...
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### Motion in one dimension and relative velocity [on hold]

Two bodies $A$ and $B$ are separated by $4~\mathrm{km}$ and $A$ is due west of $B$. If $A$ moves at a speed of $6~\mathrm{km/hr}$ towards the south, what is the relative velocity of $A$ w.r.t $B$?
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### Find the energy of an x-ray photon which can impact a maximum energy of $50~\mathrm{keV}$ to an electron [on hold]

This is an exercise question from the text book Concepts of Modern Physics by Arthur Beiser. Find the energy of an x-ray photon which can impact a maximum energy of $50~\mathrm{keV}$ to an ...
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### Invariance of a maximally entangled state under unitary operation $U \otimes U^\dagger$

Apparently the (d-dimensional) maximally entangled state, $|E \rangle = \sum_{i} |ii\rangle /\sqrt{d}$ is invariant under operations of the form $U \otimes U^\dagger$. I want to prove this result, ...
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### Derivation of expression for Berry curvature

Many texts quote the expression for the Berry curvature for a two-level system, with Hamiltonian $\mathbf{h}(\mathbf{k})=(h_x,h_y,h_z)$ in terms of $\mathbf{k}=(k_x,k_y)$, as something like \begin{...
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