# Tag Info

## Hot answers tagged magnetic-fields

4

A large magnet is indeed made up of lots of tiny magnets. In fact every unpaired electron in the material acts as a tiny bar magnet and the total field is made up by summing the individual magnetic fields of all these gazillions of electrons. You are quite correct that if you place two bar magnets alongside each other with the north poles together then they ...

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Technically, experiments involving magnetic interactions are not really "mechanical experiments". But this is not the main issue. Right after the OP quote there is a stipulation, "it is understood that the apparatuses they use for these experiments move with them". Although it might seem that the apparatus, the compass, is moving along with the person on the ...

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If you would measure the electron at one of the slits, then the interference patterns would no longer be formed. That is because the pattern is produced by interference of an electron amplitudes diffraction from slits 1 and 2. If you know that electron is at slit 1, it is of course no longer at slit 2, and therefore you wouldn't get the interference pattern. ...

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First, the physical thing we care about is $\vec B$. So we can do anything to $\vec A$ we like as long as we get the same $\vec B$. That is, we can do anything that doesn't change the curl of $\vec A$. Now, suppose that $\vec \nabla\cdot\vec A = f$. Here's where Purcell neglects to stress what he means by "analogue of $\vec E$ in electrostatics" - the curl ...

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Look at the equation $\vec \nabla \times \vec H = \vec J_{free}$, and at the same time at $\vec \nabla \times\vec B = \mu_0 \vec J$. Now, $\vec J = \vec J_{bound} + \vec J_{free}$, and $\vec H = \frac1\mu_o \vec B - \vec M$, where $\vec M$ is called the Magnetisation. $\vec H$ allows me to write the Ampere's Law in terms of free current alone, and that is ...

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$\vec{k} = k_x \hat{x} + k_y \hat{y} + k_z \hat{z}$, and $\vec{r} = x \hat{x} + y \hat{y} + z \hat{z}$; the coordinate dependence is encoded in the $\vec{r}$. These expressions are in Cartesian components, but if you ever need to calculate this in curvlinear coordinates, the logic would be the same. If $\phi$ is not specified, you can probably assume ...

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Magnetic fields certainly can influence thermal conductivity. This shows up, not surprisingly, when there is a strong influence of the magnetic field on other properties, particularly electronic ones. One (non-metal) example is 'Thermal conductivity tensor in YBa$_{2}$Cu$_{3}$O$_{7-x}$: Effects of a planar magnetic field' by R. Ocana and P. Esquinazi, Phys ...

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I don't believe that the thermal conductivity of most metals is very sensitive to magnetic fields. Yes, there will be some field-induced band shifting in the case of an itinerant ferromagnet which, in principle, leads to a change in the density of states at the Fermi level, but that will typically be a very small effect. If the magnetic field induced ...

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In principle your loop has five degrees of freedom - three for the location of the center and two for the direction it is pointing. This means you need five measurements to solve in general. If you don't know the current you need six points.

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Oh yes, at least for some values of "jam". The classic example along these lines was the measures/countermeasures struggle between Britain and Germany using magnetic mines during WWII. These mines responded to the magnetic field produced by steel-hulled ships passing overhead. The solution was to add a belt of electric cable around the ships' hulls, and ...

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Yes, if you go around N times then the emf will be N times greater than if you went around once. Why? Suppose one loop bounds a surface with area A, then N loops will bound a surface with area perpendicular to the field NA. Imagine you're looking directly through the solenoid and the surface it bounds is made out coloured glass, how many layers of glass are ...

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As you said in shunt the galvanometer is connected in series, this makes it an ammeter, An ammeter has very minimal resistance (ideally zero), So it lets all the current pass through it, causing very minimal (ideally zero) voltage drop across it

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Yes, power is lost due to hysteresis in the core. The power lost per cycle per unit volume can be calculated using the Steinmetz equation: $$Q = \eta B^{1.6}$$ and the continuous power loss (in Watts) is: $$P = \eta B^{1.6} f V$$ where $f$ is the frequency of the applied voltage and $V$ is the total volume of the core. The parameter $\eta$ is an ...

1

Iron atoms have a magnetic moment so every iron atom behaves like a tiny magnet. The magnetic field from a single atom is tiny, but in a typical ferromagnet, for example iron, the atoms line up their magnetic moments to create small aligned regions called magnetic domains. In these domains the fields from all the individual atoms adds up to produce a ...

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You can get the direction of the field without actually drawing it. The magnetic field of the current through the resistor is not just up or down. The field lines go in a circle around the resistor. You can use the right-hand rule to visualize which the way the lines go around, either clockwise or counterclockwise. If the current flows from $b$ to $a$, ...

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Use the right hand rule. Point your thumb in the direction of the current and your fingers will curl around the wire in the direction of the magnetic field. For current flowing from a to b: Your thumb points down and to the right. Your fingers will be to the left of the loop pointing downward. If you curl them around you will see that the magnetic field ...

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As long as the DC component does not saturate the core of the transformer, the (lower frequency) components of the waveform should be induced in the secondary. Consider, for example, the output transformer of a single ended class A triode audio amplifier Image credit In this case, the primary current is 'pulsating' DC, i.e., the primary current varies ...

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Yes surely, The pulsating DC is impure dc. Each pulse will be creating a change in magnetic flux in the transformer core. If you see the normal ac diagram the wave from 0 to T, It is similar to your pulsating DC diagram, there is a change in flux in transformer in this case. But it interesting to note that the transformer will give the increased or ...

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In effect, it's done all the time in a transmission electron microscope. Usually it's not a simple double slit but rather a multiple slit (in the form of a crystalline lattice). This is happening in the presence of a strong and rather inhomogeneous magnetic field, produced by the microscope's objective lens. The interaction (and remember, it is an ...

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"The frequency doesn't change" is only true when the core is perfectly linear. For a real transformer, there will be some nonlinear effects (saturation) meaning that the sinusoidal input waveform will create harmonics in the output - second harmonics and higher frequencies will appear. But if you ignore those, then the flux change will vary sinusoidally at ...

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since you are concerned about a long solenoid, this problem has a very simple solution. Suppose you have two identical long solenoids, each of them having magnetic field $B$ at the ends. You join them end to end, such that their magnetic moments are in same direction. Thus, at the junction the magnetic field adds up to $B+B=2B$. But this junction is ...

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Not completely clear from your description, but do you mean that you tuned your frequency to achieve a current resonance and then inserted the iron core? Did you not consider that the resonant frequency is completely changed by the increased inductance, so you would then be far from resonance at the same frequency? Depending on the resistance in the ...

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Use the equation of Lorentz force to calculate the field vector. Quoting from this link, If a particle of charge $q$ moves with velocity $v$ in the presence of an electric field $E$ and a magnetic field $B$, then it will experience a force $$\mathbf{F} = q\left[\mathbf{E} + (\mathbf{v} \times \mathbf{B})\right]$$ In your case, there is no electric ...

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