All Questions
Tagged with electromagnetism homework-and-exercises
1,551
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2
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1
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479
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Transformators (primary and secondary windings)
Consider the following problem:
Robby wants to put a light in the shed so he puts a cable between his house and the shed. In the cable there are 2 wires with a combined resistance of $0,92 \space \...
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2
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504
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Show that $\partial_\nu T^{\mu\nu} = - j_\nu F^{\mu\nu}$
In a theoretical physics homework problem, I have to show the following:
$$\partial_\nu T^{\mu\nu} = - j_\nu F^{\mu\nu}$$
Where $T$ is the Energy-Momentum-Tensor, $j$ the generalized current and $F$ ...
- 8,439
1
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1
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Magnetic force on capacitor
I have this problem: I have a capacitor formed by two parallel square-shaped plates, of side $a$, and with distance $d$ between them. They're asking me out of other things, the magnetic force as a ...
- 1,433
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1
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Write $\epsilon_{\mu\nu\alpha\beta} F^{\mu\nu} F^{\alpha\beta}$ as a total divergence $\partial_\mu G^\mu$
I have the following homework problem in theoretical electrodynamics:
Show that the gauge invariant Lagrange density $\epsilon_{\mu\nu\alpha\beta} F^{\mu\nu} F^{\alpha\beta}$ can be written as a ...
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3
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3
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What is the current through the lamp?
We have the following circuit:
A neon lamp and a inductor are connected in parallel to a battery of 1.5 $V$. The inductor has a 1000 loops, a length of $5.0 cm$, an area of $12cm^2$ and a ...
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3
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2
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The direction of the Lorentz Force
We have a square loop (I believe it's called) in a uniform magnetic field between the 2 poles of a permanent magnetic field (green is N, red is S). P is connected to the positive pole of a voltage ...
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5
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1
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What is the change in flux through a loop that has been rotated?
We have a number of field lines perpendicular to one loop of wire with an area $A = 10\textrm{ cm}^2$. The magnetic field is$B= 7.2\times10^{-5}\textrm{ T}$.
You turn the loop and the flux decreases ...
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2
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Hamiltonian and non-conservative EM force
I have to find the Hamiltonian of a charged particle in a uniform magnetic field; the potential vector is $ \vec {A}= B/2 (-y, x, 0)$.
I know that $$H=\sum_i p_i \dot q_i -L$$ where $p_i$ is ...
- 1,133
2
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4
answers
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charge density in a wire
If we have a infinitely thin and infinitely long straight wire on the $z$-Axis with given current $I(t)$, how can I compute the charge density?
I figured out that the current-density is given by $\...
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votes
1
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Point where resulting magnetic field is equal to 0
I am trying to solve the following task
Given 3 infinitely long current carrying wires, as shown on image ($I_1=I_2$ , $I_3=2I_1$) and $r=5 cm$ calculate the point between them (in the same plane; ...
user16688
3
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1
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CGS Units to SI Units
This may be a stupid question but I am having trouble getting the same result in CGS units as I would if I used SI units for a unitless calculation.
I have to calculate $E_\mathrm c=\frac{m_\mathrm ...
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1
answer
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A point in multiple magnetic fields
Given two parallel wires carrying a current (e.g. 2 and 3 Amperes) and the distance between them, 5 cm, how do I determine the magnitude of the magnetic field at a point M mid-distance between the ...
user16688
2
votes
1
answer
96
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Why does $H_2$ form on such a long time scale?
If we were trying to figure out the time scale for a gas-phase reaction between two hydrogen atoms in a molecular cloud (which has density $~10^4/$cm$^3$), apparently the reaction would happen on a ...
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Force on Earth due to Sun's radiation pressure
I have been asked by my Classical Electrodynamics professor to calculate the force that the Sun exerts in the Earth's surface due to its radiation pressure supposing that all radiation is absorbed and ...
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