All Questions

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Period of small oscillations of rotational disk [on hold]

This is a question on a university physics exam paper, and it doesn't seem immediately intuitive how the problem works. The answer is given, but not any details of the working. Also, I'm not sure if ...
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What happens to the emf generated due to a change in magnetic flux in a coil?

When we move a magnet into a coil of wire (open circuit) and then out of it, we create a emf across the ends of the coil and another emf in the opposite direction. My question is what would happen to ...
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Gravitational force of a ring [on hold]

Given a ring with mass $m_1$, radius $R$ and a point mass $m_2$ with distance $x$ regarding the center of the ring. How can I calculate the gravitational force of this ring ? At first glance I'd say ...
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Timescales for isothermal processes

My understanding is that processes in ideal gases need to take place over relatively long timescales to be idealised as "isothermal" such that the gas temperature can be assumed not to change. For ...
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Planck's law versions: intensity vs energy density vs spectral radiance

Here it shows there are three (considering only the wavelenght or frequency cases) ways of writing Planck's law. I am trying to derive them from one another. I converted from spectral radiance ...
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Photons under pressure

Does it make sense for photons to be put under pressure, if so how would this be measured? I'm wondering because I would like to plug in $E = h\nu$ into the formula for enthalpy.
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Which technique is used to measure huge astronomical distances which are in terms of billions of light years? [duplicate]

I know what a "light year" means. However, I am very curious to know about the technique through which scientists are able to calculate the distance of various astronomical bodies from earth which are ...
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A circuit with a solenoid and no resistors

We have an electric circuit consisting only of a solenoid (its two ends are connected). Let's suppose that the total length of wire used is $l$ and the wire has a cross-section of area $S$ and ...
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Special relativity revisited [on hold]

I had a query about Einstein's special relativity, particularly when it came to the notion of $c$ being the ultimate speed. I resolved such a query by treating an imaginary particle traveling at an ...
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Why must the deviations from equilibrium be small for zero difference in energy in this solenoid?

A long solenoid with a square cross-section is partially immersed in a magnetic, non-conductive liquid of permeability $\mu$. The solenoid's axis is parallel to the liquid's surface. ...
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Derivation of Maxwell's equations [on hold]

I derived the equations of Maxwell in a current free medium, last year about this time (I need help editing this). I made use of complex quantities, and Cauchy-Riemann relations. In this derivation ...
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How come a current sheet of $J_s = J_0 \hat{x}$ produces plane wave solution?

Given in the picture. There is a current sheet $J_s = J_0 \hat{x}$. Supposedly Jo is not oscillating. So, how does this thing create a plane waves propagating away from the current sheet? Shouldn't ...
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Where does mass go when energy is converted in to photons?

If matter and anti-matter annihilate each other they emit a photon with the energy that corresponds to the mass, right? This is the best example I could think of matter/energy being converted directly ...
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Relativistic doppler effect in three dimensions

Consider a sphere that travels through space with a velocity $v$. I wish to investigate the relative intensities of the CMB on all points on the sphere. For the microwaves approaching from the direct ...
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Smallest Black hole nessesary to devour Earth?

While looking into black holes I can across the idea of hawking radiation, and the fact that microscopic black holes would near instantaneously evaporate before doing any damage. However larger black ...
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effective field theory of the projective semion model

The "projective semion" model was considered in http://arxiv.org/abs/1403.6491 (page 2). It is a symmetry enriched topological (SET) phase. There is one non-trivial anyon, a semion $s$ which induces a ...