All Questions
10
questions
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What is the physical meaning of the torque term involving the magnetic displacement force?
In Zangwill's Modern Electrodynamics the magnetic torque is derived in Eq. 12.63 to be
\begin{equation}
\mathbf{N}(\mathbf{r}_0) = \mathbf{m} \times \mathbf{B}(\mathbf{r}_0) + \mathbf{r}_0 \times \...
2
votes
1
answer
112
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Why can we calculate force on a dipole from torque?
In the Feynman lectures he derives the (mechanical) energy of a dipole
$$ U = -\boldsymbol{\mu}\cdot \boldsymbol{B} + \mathrm{constant}$$
by considering only the torque on it in a uniform field. He ...
- 2,122
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votes
2
answers
28
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Couple acting on quadrupole due to a point charge
I wish to find the couple acting on the quadrupole due to q', assuming r>>a. Here is my working:
Force acting on -2q:
$E_{at \ -2q} = \frac{q'}{4\pi\epsilon r^2} \\
F_1 = (-2q) E = \frac{-2qq'}{...
- 126
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47
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Torque on a current loop in a magnetic field, could you please explain the derivation and concept?
Torque=mxB
Consider a rectangle loop pqrs of sides l and b , where pq and RS are perpendicular to field , I is the current, B is field , imagine that this loop is placed between 2 magnets.
Force ...
0
votes
1
answer
34
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Force (linear and rotation) field between two magnets [closed]
Say I have the magnetic field of two magnets $S_1$ and $S_2$ as well as their respective magnetic moments. Each of their field strengths is modeled by a series of vortexes on a 2d plane. What is the ...
- 3
0
votes
1
answer
967
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Force on a current carrying loop in a non-uniform magnetic field
I was taught that a current carrying loop in a non-uniform magnetic field will always experience both a torque and a net force.
Is this always true? I can't think of any examples where the force would ...
- 256
2
votes
2
answers
915
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How is force transmitted across a body?
So I am leaning about various topics like physics like simple machines, center of mass, momentum, energy conservation, equilibrium but the more I study these "upper" level concepts the more ...
- 813
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1
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58
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Why astatic needles are immune to only terrestrial magnetic fields and not other magnetic fields?
This web article says:
Astatic needles are basically two needles of approximately the same magnetic strength, mounted on top of one another. They are parallel, but their magnetic poles are on ...
- 137
1
vote
2
answers
221
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Torque in state transitions in the Bohr model
We know that in the Bohr model, angular momentum is quantised as $L= n\hbar = nh/(2\pi)$. So when an electron jumps from one state to another, its angular momentum certainly changes, which means that ...
- 409
1
vote
1
answer
311
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How is Magnetic force on a current carrying conductor $Blb$
I was reading an answer about torque acting on a rectangular current carrying loop kept in a uniform magnitude field B.
Force acting on each sides is $F_1$, $F_2$, $F_3$, $F_4$.
It's written here : ...
- 133