All Questions
Tagged with electromagnetism homework-and-exercises
1,551
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In which of the above figures will the light bulb be glowing?
What is principle of solution behind this induction problem (problem 29)? The problem can be find in here (problem 29).
Problem is:
The five separate figures below involve a cylindrical magnet and a ...
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Instantaneous current after battery unplugged in RL circuit?
I've been racking my brain over this, and I can't find any clues in my textbook as to how to approach it.
I have the following circuit:
My goal is to find R such that, right after the switch is ...
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So do I use this Lorentz's law or which law do I use?
I have difficulty understanding exercise 24 in this document:
Two parallel wires I and II that are near each other carry currents i and 3i both in the same direction. Compare the forces that the two ...
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Bandgap Spacing in Photonic Crystals
I am doing some self-study on photonics and have encountered the following question:
We know that amorphous electronic crystals such as amorphous silicon have a bandgap. Can amorphous photonic ...
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Find magnetic scalar potential for superconducting sphere
In regions where $J = 0$, the curl of the magnetic field $B$ is necessarily zero (since $\nabla \times B = \mu_0 J$). Therefore $B$ can be written as $B = -\nabla V_m$, where $V_m$ is a scalar ...
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Deriving the Poynting Theorem
I am trying to derive the Poynting theorem. So far, I've only been able to narrow down which equations I think I'll need to do so. These are the equations:
Maxwell's Equations:
$$
\nabla\times{\bf E} ...
- 283
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Charge, velocity-dependent potentials and Lagrangian
Given an electric charge $q$ of mass $m$ moving at a velocity ${\bf v}$ in a region containing both electric field ${\bf E}(t,x,y,z)$ and magnetic field ${\bf B}(t,x,y,z)$ (${\bf B}$ and ${\bf E}$ are ...
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Shouldn't the electric field in a solid insulating sphere be linear with radius?
I am a senior in High School who is taking the course AP Physics Electricity and Magnetism.
I was studying Gauss's laws and I found this problem:
A solid insulating sphere of radius R contains a ...
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Inductance - Sign convention problem
My problem is with a circuit containing a resistor of suitable resistance $R$ and a solenoid.
Initially, a battery is connected which generated a current in the circuit and at $t=0$, the battery is ...
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Where does the equation $E_q = \frac{kq}{r^2}$ come from in this problem?
A point charge is placed at each corner of a square with side length
$a$. The charges all have the same magnitude $q$. Two of the charges
are positive and two are negative, as shown in the following ...
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How to get an integral formula for the flux time derivative
$$\frac{d}{dt}\int \limits_{A} \mathbf B d \mathbf A = \int \limits_{A} \left( \frac{\partial \mathbf B}{\partial t} + \mathbf v (\nabla \cdot \mathbf B ) + [\nabla \times [\mathbf v \times \mathbf B ]...
user8817
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Finding the charge density
I can't figure out how to find the charge density for the following problem:
A conductor is placed in an external electrostatic field. The external
field is uniform before the conductor is placed ...
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Calculating equation of motion from action
Suppose my action integral is $$S=\int d^4x(\nabla \times A)^2$$ and $\delta S$ gives $$\delta S =\int d^4x [2(\nabla \times A).(\nabla \times \delta A)]$$
I would like to calculate the coefficient of ...
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The force exerted by a ~10 Tesla magnet on a C13 isotope?
How much force would a ~10 Tesla magnet exert on a weakly magnetic C13 isotope? If I made a molecule of diamond with $N$ C13 atoms, how large would $N$ need to be for me to pull on it with something ...
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Calculating the magnetic flux density of a thin, flat conductor
I am currently preparing for a physics exam and I have troubles understanding how to solve the following exercise:
A current that has the constant current density $\vec{j}$ flows through a thin, ...
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