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    Balance of forces: confusion

    1. Homework Statement 2. Homework Equations So I basically have to establish the non linear differential equation that governs the movement of this robot (relates d and theta): 3. The Attempt at a Solution So I know that we should have the sum of torques equal to...
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    Confusion about the direction of the vectors: motional EMF

    1. Homework Statement I'm working through an example with motional EMF and I'm having trouble understanding the directions of vectors so that I can apply induction law. The magnetic circuit seems complex because the circuit is used to analyze other situations but the air gap 3, the coil 3 and...
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    Mutual inductance coefficient with so little info

    Holy cow I just checked the document with the books mistakes and yup it should only be a symbolic result. Well at least all this time made me understand the dot notation which I wasn't really understanding so thanks :)
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    Mutual inductance coefficient with so little info

    I'm only told that I have a sinusoidal current but not a single value is provided... There must be another way :/
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    Mutual inductance coefficient with so little info

    Ok, so I looked on some tutorials on the internet and I'm more familiar with the concept now. This leads me to obtain: $$ \frac{\psi_1 \psi_2}{I}=L_1 + L_2 - 2 |L_M|$$ Where I take the absolute value to reinforce that we have discordant coupling (because of that the value of the mutual...
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    Mutual inductance coefficient with so little info

    No I haven't :/ That's why I'm missing something here. I came across the formulas for coupling inductors: $ L= L1 + L2 + 2M $ $L = L1 + L2 - 2M $ And didn't understand where they came from and the meaning of them. Maybe it has something to do with that dot notation? Do you know where I can...
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    Mutual inductance coefficient with so little info

    I meant that B is directed to the right on the windings on the right and to the left on windings on the left! I'm sorry I'm not getting there, what does place the dots even mean?
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    Mutual inductance coefficient with so little info

    For what I understand it is leftwards on the left windings and rightwards on the right windings, correct?
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    Mutual inductance coefficient with so little info

    1. Homework Statement I have the following circuit: The two inductors are connected in series are characterized by internal resistances R1 and R2 and self-inductances L11 and L22. The magnetic coupling factor between the inductors is k = 0.75. The inductors carry the same current i. What...
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    Two voltmeters in parallel measure these different voltages

    1. Homework Statement I'm currently studying induction law and circuits with inductors. I came however with the following circuit: [1]: https://i.stack.imgur.com/ghaiE.png 2. Homework Equations 3. The Attempt at a Solution Now my text says the following: "Unlike what your intuition...
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    Magnetic energy stored in a cylindrical conductor

    The goal of the exercise is to do the opposite e.g. determine E and then use that formula to get L. I didn't post that last bit because it was not relevant for the question I guess.
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    Magnetic energy stored in a cylindrical conductor

    1. Homework Statement So I came across with following problem: > Consider a cylindrical conductor of infinite length and circular section of radius a and that is traversed by a stationary current I. What is the magnetic energy stored in the conductor. 2. Homework Equations 3. The Attempt...
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    Energy in a rotating square loop

    Substituting the values on I expression we obtain ##I=1.26 \sin(200 \pi t)##. Substituting in P we get to ## P=31.752 \sin^2(200 \pi t)##. Then ##\int_{0}^{120} 31.752 \sin^2(200 \pi t) dt = 1.9 kJ## So that's it...
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    Energy in a rotating square loop

    Well than again since they only asked for the energy dissipated by Joule heating, we don't have to count with other forces (e.g.. rotating the circuit). I don't understand why I'm getting half of what I was supposed to though...
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    Energy in a rotating square loop

    1. Homework Statement A square circuit of resistance R=20Ω and side ℓ = 0,2 m spins 100 times per second around an horizontal axis that splits it in two. There is an uniform magnetic field B=1T perpendicular to the position ocupied by the circuit at t=0s. Calculate (1) the magnetic flux, (2)...
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    Magnetic field in the case of a thin magnetized cylinder

    But isn't ##2 \pi L ## also a length? Its the "path" the the current takes, right? Oh so because I'm integrating ##I \, dl## in Biot Savart if I used that perimeter when computing I it would be like multiplying by the same thing twice...
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    Magnetic field in the case of a thin magnetized cylinder

    Ok that gives me the right answer. But now I understand what I'm not figuring out. Why are you only using the thickness of the cylinder to calculate I. Shouldn't we also use the perimeter? I know in terms of units we should only use one (to cancel out the m^-1)... But why using the thickness and...
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    Magnetic field in the case of a thin magnetized cylinder

    Oh so he ring approximation is the way to go right? For $I$ I got 6.3 A (as I described above multiplied the current density by $2 \pi R l$ where R is the radius and l the thickness. For $\mu_0$ I used $4\pi \times 10^{-7}$
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    Magnetic field in the case of a thin magnetized cylinder

    My other guess was that this degenerated in the case of a ring of charge (current only superficial on the sides and neglect thickness). But that would give me a field of $$B=\frac{\mu_0 I}{2R}$$ and that would lead me up to a field 39.584 mT...
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    Magnetic field in the case of a thin magnetized cylinder

    But all of my current is that superficial bound current, right? There is no free current. So my full current will be $#10^5 \times 2\pi \times 1 \times 10^{-2} \times 1 \times 10^{-3} = 6.3 A#$ As for the B field. I'm having a bit of trouble applying Biot Savart. So I have Having dl the...
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    Magnetic field in the case of a thin magnetized cylinder

    1. Homework Statement Consider a cylinder of thickness a=1 mm and radius R = 1 cm that is uniformly magnetized across z axis being its magnetization M= 10^5 A./m. Calculate the bound currents on the cylinder and, doing convenient approximations, the B field on the axis of the cylinder for z=0...
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    Volume ratio in an adiabatic gas expansion

    @TSny I want to apologize for my reaction on the other day. I was very stressed because I've been working for hours not figuring out how to solve the problem. Not that that can justify my rudeness. So my sincere apologies. I eventually figured out what yo meant with the hint that it was an...
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    Volume ratio in an adiabatic gas expansion

    @TSny if you want to be vague and leave without further explanations, please leave.
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    Volume ratio in an adiabatic gas expansion

    Yes I know that means the variation of internal energy is just the work done but how does that help...
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    Volume ratio in an adiabatic gas expansion

    1. Homework Statement Consider a perfect monoatomic gas at pressure $p_i$ 1.2 atm and temperature $T_i$ 300K, that is in equilibrium inside a cylinder having a volume $V_i=1L$ and which piston has a mass of 1kg and is at an height of 50 cm. Admit that a mass M=3.13kg is over the piston. When...
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    Coaxial cable conductors with dielectric: polarization of charge

    Yes what I did was I took my expression for ##V##, isolated ##\lambda## in that expression and substituted in my expression for ##P##. That was how I got to my expression for sigma (with a minus sign). If I substitute V back to my sigma expression I will have: $$\sigma= -\frac{\lambda...
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    Coaxial cable conductors with dielectric: polarization of charge

    But if R1 is in the denominator then I will not get to the answer. Do you know how should I proceed?
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    Coaxial cable conductors with dielectric: polarization of charge

    1. Homework Statement Consider a coaxial cable which consists of an inner cylindrical conductor of radius R1, and a shell cylindrical conductor of radii R2 and R3. The 2 conductors are separated with a dielectric material of permittivity ε. Consider the length of the cable, ℓ, much larger than...
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    Total charge dielectric

    Oh! The volume of the shell is $$dV=4\pi r^2 dr$$. This way I get to the total charge equaling zero. Thank you very much!
  30. G

    Total charge dielectric

    1. Homework Statement Consider an infinite environment with electrical permittivity non-homogeneous $$\epsilon=\epsilon_0(1+a/r)$$ a being a positive constant. A conducting sphere of radius R and charge Q is put on that environment, centered at r=0. Determine the electric field $$E$$, the...
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