# All Questions

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### Gauss law problem

Consider a cube in an variable electric field such that there is no charge enclosed by the cube.Say E = ax^(1/2) (where a is constant) (Base of cube is in the xz plane) and its direction is parallel ...
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### Number of electrons in conduction band

As mentioned in a previous question, the number of electrons in conduction band in a semiconductor can be computed as follows: $$N = \int_{E_c}^{+\infty} g_c(E)f(E)dE$$ where $g_c(E)$ is the density ...
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### Standing Waves due to 2 waves of different amplitude

If I have 2 waves of different amplitudes, but same frequency and direction, traveling in opposite directions towards each other, let's say transverse waves on a string formed due to partial ...
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### Why don't the magnetic dipole moments in a neutron cancel out?

This may be a silly question. I thought magnetic dipoles were dependent on electric charge, so why in a neutron do the dipole moments not just cancel each other out?
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### Prove that an electron in a hydrogen atom doesn't emit radiation [duplicate]

According to electrodynamics, accelerating charged particles emit electromagnetic radiation. I'm asking myself if the electron in an hydrogen atom emits such radiation. In How can one describe ...
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### Spontaneity / Free Energy of Non-Isothermal Process

I'm trying to determine a lower bound for the work input necessary to make an entropy-reducing process "spontaneous" in the sense that the 2nd law is not violated. For a constant temperature and ...
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### How to intuitively understand susceptibility formula?

When calculating various susceptibilities, we get below formula again and again. \chi \left( {q,0} \right) \sim \sum\limits_{\bf{k}} {\frac{{{f_{\bf{k}}} - {f_{{\bf{k}} + {\bf{q}}}}}}{{{\varepsilon ...
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### Is it possible to “see” atoms?

As per my knowledge, atoms are small beyond our imaginations. But there is an image on Wikipedia that shows silicon atoms observed at the surface of silicon carbide crystals. The image: How can we ...
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### Why do charge on an object remains unaffected by the motion of the object?

Unlike mass, the charge on an object is said to be unaffected by the motion of the object. This statement in my text book, is not yet understood by me. I don't know theory of relativity. On ...
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### Intuition behind deriving the FRW metric [on hold]

I am studying the FRW metric and am looking at a motivation for it here. The motivation seems to use four spatial dimensions. Why do we need the fourth spatial dimension in this? This doesn't seem ...
Why does the attractive Dirac Delta distribution (function) potential $V = \alpha\delta$(x) (for negative $\alpha$) yield both bound AND scattered states? Is this due to the definition of the Dirac ...