Dear all.
I would like to know the general expression of the ratio of the electric field strength E to the magnetic flux density B. I know E/B = c, where c is the speed of light, for a vacuum, but I want to know if this is stil valid for any material where the electric and magnetic fields are...
Hello.
I'm sorry but I don't understand your geometry.
The circumferential magnetic field around the conductor will induce a voltage on another wire which is in parallel oto the first conductor? This EMF is very different than what I'm used to such as a solenoid coil so I don't get how EMF is...
Hello.
I'm using CT (Current Transformer) to measure the current flowing on the power line. The frequency of the current is 13.56 MHz. CT appeared to be metal-shielded (This metal case of CT may be grounded when CT is used).
CT has a toroidal shape and the power line under the measurement...
Thanks for replying very quick comment!
So, E or B-fields in Maxwell's equations are all the same one, in fact.
Could you help me a little bit more? I actually want to derive that RHS of \nabla \cdot E = \frac{\rho }{{{\varepsilon _0}}} is zero when E-field here is E-field accompanied with...
Hello.
I would like to ask one simple question. Do we need to distinguish E-field (Electric field) in Gauss's law from those in Maxwell-Faraday equation and Ampere's circuit law? I firstly thought that E-field in Gauss's law is only for electrostatics so I need to distinguish it from E-field in...
Hello.
I really appreciate your help!
I've summarized what I've studied for the relation between Faraday's law of induction (or simply called Faraday equation) and Maxwell-Faraday equation. I found that the Faraday equation describes not only Maxwell-Faraday equation, but also magnetic Lorentz...
Hello. Thank you for a quick reply!
Well..in 2nd answer, how to derive the original Faraday equation from the differential form of MF (Maxwell-Faraday) Equation? Applying stokes' theorem to this MF equation only gives MF equation in an integral form where ∂/∂t is inside the integral, while the...
Hello.
I have several confusions regarding Faraday's law of induction.
EMF = \int_{}^{} {\vec E \cdot d\vec l} = - \frac{{d\Phi }}{{dt}} = - \frac{d}{{dt}}\int_{}^{} {\vec B \cdot d\vec S} . It means that If the magnetic flux Φ through the closed conducting loop changes in time, electric...
Hello.
I'm trying to do my best to explain your question. I can be wrong:)
By rubbing a glass rob with a silk, some electrons in the rob transfer to the silk due to different electronegativities of both materials, I guess. As a result, the rod becomes positively charge as it has a lack of...
Yeah...the electric field vector E = -∇φ where φ is the electric potential, so field lines are determined only by the variation of the potential over the space, not depending on absolute values of it. I see.
Maybe there is something I missed from what the lecturer said.
Hello.
I'm now taking accelerator physics class and the lectures said in the thermionic electron gun, anode metal mesh should be grounded in order to prevent electrons which traveled beyond the mesh from coming back due to the electric field lines.
Without grounding of the anode, I believe...
Hello answerers
Thanks to give me very clear point. As Collisional frequency formula is equal to speed of an incident particle/mean free path of that particle, so it is average value of collisional frequency for a particle, not sum of all collisional frequency for all incident particles.
I...
I'm sorry but I found the answer immediately.
V = kg⋅m2⋅s-3⋅A-1 (https://en.wikipedia.org/wiki/Volt)
Substituting V into m2/V⋅s gives C⋅s/kg.
Problem is solved:)
Hello.
Electron mobility in plasma is μ = q/m⋅ν, where q, m and ν are charge and mass of electron and electron collisional frequency. (https://en.wikipedia.org/wiki/Electrical_mobility)
And unit of the mobility is m2/V⋅S (https://en.wikipedia.org/wiki/Electron_mobility)
According to the...
Hello.
The collisional frequency is generally expressed by ν = nt×average of (σv), where nt, σ and v are density of target (atoms or molecules), collisional cross section of target and kinetic velocity of incident particles. σ depends on kinetic energy of incident particles
I thought...
Hello.
Let's say lossless case where AC voltage source connects to inductor in series. As current increases, energy is stored in form of magnetic field within the inductor. When current decreases, stored energy is released. Question is where this energy goes? Since there is no load and system...
Yes, it is potential difference. In electronics, we usually call this quantity as voltage. When we say voltage, for example, 5 V, it is the potential difference between two point. Normally when electronics is powered from power line, not battery, ground (connection to earth, I mean surface of...
I also wish I would get these parameter precisely, but in practice, It is not easy. Anyway thank for commenting me.
Okay then I have one quite definite question for you. Does current see net voltage over the surface or they can see local phenomena? I'm asking average voltage over the surface is...
Well..what about this? If ground point for external surface is only one and voltage is fluctuated over the surface in spatial varying. Thus maybe there is current flow on the ground wire to the point due to induced local voltage rise?
Thanks for replying.
Thus I interpreted your reply that radiation taken inside the cage would cause strong current flowing over inner surface of the cage but as they have skin effect, current flowing outside is much smaller thus voltage is not fluctuated much on outside surface? On outside...
Hello.
I'm sorry to reply lately. Any reference voltage is possible here. As long as voltage measured on certain point of the cage is steady. We could see constant voltage which magnitude is depending on the reference voltage. If not, we could see voltage fluctuation. Let's say we can use some...
Thanks. You mean capacitor is to be added between wire of A (or B) and ground plane? capacitor is usually passes for high frequency like high frequency filter thus...what feature I can expect to this job? And do you think adding capacitance lower down pulse rising time that is actually not what...
Thanks for replying.
Thus..if wavelength of the signal is very long compared to the ground plane, we can say it is steady-state picture and all points on the ground plane are to be the same at a time? means voltage of all plane is varying in time without spatial variance like quasi-steady state...
Hello.
Let's say we build the Faraday cage which surround strong radiation such that no radiation can escape to outside world for safety.
What happens on external surface of the Faraday cage in voltage during shielding? Is it fluctuated?
Oh thanks. this is really great picture! This picture clearly confirms that in transient time voltage drop along straight path from A to B is the most strong. Thanks!! I'll refer this for my future electronics enclosure design. Anyway...Could you tell me how you get this image?
Hello.
The ground plane is sometimes used as current return path. If current is low frequency and amplitude is small then voltage rising due to current flow can be ignorable.
However, what is return current is actually very high in both frequency and amplitude? In our lab, gas discharge...
I don't know what small wavelength means for electrons. The electron beam can be scattered from the material as they pass through. But we don't say it is refracted as Snell's law for light.
The collective means electrons are moving as a fluid. they're communicated with each other due to long range feature of column force. You better study critical frequency in internal search. plasma frequency is the frequency what I mean and you can easily find relevant info for it.
Anyway why...
Actually for my last reply in this post, I've found that silicon PN junction depletion layer voltage (due to space charge) or built-in voltage is about 0.6 V. That is why this number is given as firstly suggested by NascentOxygen since this voltage must be overcome to current flows. Although I...