# Search results

1. ### Ratio of the Electric field to the Magnetic field

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...
2. ### How a TFP (Thin Flim Polarizer) works?

Hello. I've been really curious about how TFP (Thin Flim Polarizer) works. I've searched TFP information through the Internet which tells that TFP utilizes Brewster's angle. This explains how the P-polarization transmits TFP with 100 % transmission, but I don't know how the S-polarization is...
3. ### I What is the origin of Van der Waals force?

Hello. What I know about the Van der Waals force is that it comes from an instantaneous electronic cloud flucutation of the netural atom. This instantaneous electric dipole of the atom attracts electrons in nearby neutral atoms so other electric dipoles are induced on those atoms. As a result...
4. ### I Is a quasi-static but irreversible process possible?

Hello. I read the textbook of the thermodynamic and it said the definition of the reversible process as "thermodynamic process which is slow enough so the system state is always infinitesimally close to the thermodynamic equilibrium (quasi-static) during the process. Such a process can always...
5. ### Why is entropy a state variable even for irreversible path?

Hello. The entropy S is a state variable or state function as the integral of dS = dQ/T is a path-independent, provided that the path is reversible process path. However, such a path-independency of the integral breaks down when the path includes irreversible process. So, I guess we can only...
6. ### In 3rd step of Carnot cycle, work done on the piston is pdV?

Hello. First, look at the figure describing Carnot's cycle. In 1st step (A → B) and 2nd step (B → C), I fully understand that the work done on the pistol (surrounding) by the gas (system) is dW = pdV where dV = Adl since F = pA is the only force on the pistol from the gas (I assumed there...
7. ### Can a time-varying magnetic field pass a metal sheet?

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...
8. ### Why is EMF (ElectroMotive Force) equal to a voltage?

Hello. Let's say a current i(t) flows through an inductor of solenoid type. Time-varying i(t) generates a magnetic field B(t) inside the magnetic core of the inductor. As B(t) is time-varying, EMF, which is the line-integral of the induced electric field E(t) along a coil (which carries i(t))...
9. ### Is there microscopic version of general Ohm's law of V=IZ?

Hello. Resistive Ohm's law is famously known as V = IR. We can derive its microscopic version as being followed. V = El, where E and l are, respectively, an electric field and a resistive load length over which a voltage drop V is developed. I = JS, J and S are a current density and a...
10. ### Identities of fields in Maxwell's equations

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...
11. ### Magnetic flux and current directions of transformer

Hello. Let's take a transformer picture first. The basic equation explaining how the transformer work is the equation of Faraday's law of induction. \begin{array}{*{20}{c}} {{V_P} = - {N_P}\frac{{d{{\rm{\Phi }}_B}}}{{dt}}\;\;\;\;\left( 1 \right).}\\ {{V_S} = - {N_S}\frac{{d{{\rm{\Phi...
12. ### Some confusion of Faraday's law of induction.

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...
13. ### How does an equivalent impedance consume a real power?

Hello. Please looks at the attached image first. The left image is LCC impedance matching network (one of T-type impedance matching networks) and the right is the corresponding equivalent circuit when CT and CL are adjusted such that an equivalent impedance of the sub-circuit surrounded by...
14. ### Impedance matching concerns equivalent impedance of circuit?

Hello. Please look at the attached image first. There are two circuits A and B which have individual electrical components a and b. Components a and b are electrically and directly connected by the red lines. Impedances of individual components a and b are not matched, however, equivalent...
15. ### I'm thinking about 2nd Ph.D. for particle physics

Hello. I'm actually taking Ph.D. course for plasma physics and I think I'll finish this course within this year. I took classes in quantum field theory and general relativity in last semester luckily and experience of these subject ignited a desire to study theoretical particle physics and...
16. ### I Common eigenfuctions for degeneracy

Hello. I read the textbook and found that common eigenfunctions are even possible for degenerate eigenvalues. Let's say operators A and B commutes and eigenvalue a of operator A is N-fold degenerate, means that there are N linearly independent eigenfunctions having same eigenvalue a. These...
17. ### A Paschen notation for electronic states of Argon atom

Hello. I think excited states of Argon atom is described by j,l coupling written as (2s+1)[K]J. However, when I read some papers describing cross section data for Argon atom, data are quoted with strange notation, Paschen notation. I tried to study the Paschen notation and found that its form...
18. ### I Total angular momentum for antiparallel electrons

Hello. Let's have two electrons with same orbital quantum number li and these electrons are in antiparallel; one electron has magnetic quantum number mi = a and and other electron has mi = -a (but we don't know which one has ml = a as we're in coupled representation to talk about total angular...
19. ### A A problem about branch cut in contour integral

Hello. I have a difficulty to understand the branch cut introduced to solve this integral. \int_{ - \infty }^\infty {dp\left[ {p{e^{ip\left| x \right|}}{e^{ - it\sqrt {{p^2} + {m^2}} }}} \right]} here p is a magnitude of the 3-dimensional momentum of a particle, x and t are space and time...
20. ### I Domain of single-valued logarithm of complex number z

Hello. Let's have any non-zero complex number z = reiθ (r > 0) and natural log ln applies to z. ln(z) = ln(r) + iθ. In fact, there is an infinite number of values of θ satistying z = reiθ such as θ = Θ + 2πn where n is any integer and Θ is the value of θ satisfying z = reiθ in a domain of -π <...
21. ### A Wave of an outgoing anti-particle in quantum field theory?

Hello. I'm studying a course of the Quantum Field Theory and I got a question in a canonical quantization of a scalar field. I don't write a full expression of the field quantization here but the textbook said terms with ei(p⋅x - Ept) are associated with an incoming particle and terms with...
22. ### What do electric field lines look like for two metal plates?

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...
23. ### I Why is association rule in angular momentum sum not valid?

Hello. The quantum mechanics textbook shows the relation of J1 + J2 + J3 ≠ J1 + (J2 + J3). I believe Ji is total angular momentum operator for ith group of electrons (but actually I have not seen J1 operator while I have seen J12 operator so far). I don't know how to prove J1 + J2 + J3 ≠ J1 +...
24. ### I Why are total orbital QN l,m zero for closed subshell?

Hello. Here, I'm asking why total orbital quantum number l and total magnetic quantum number m are zero for closed subshell in atom. Let me review the addition of angular momentum first: Each electron has its own orbital quantum number li and magnetic quantum number mi. Then for two electrons...
25. ### I Could you provide me a selection rule?

Hello. When I accessed to selection rule page in Wikipedia, I have a difficulty of how to use rules listed there. I'm now only concering electric dipole transition so column (E1) in the table there will be my only interests. Since I need to know whether transition is possible or not between...
26. ### How to confirm unit of electron mobility as m^2/(V*S)?

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...
27. ### Is collsional frequency actually frequency per an electron?

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...
28. ### I Why does high surface energy of the solid have more wetting?

Hello. Recently, I have read the article about plasma surface treatment. The article says contact of the plasma to the surface of the sample increases surface energy by transferring plasma energy to the surface. Then it is suddenly saying that wettability of some industrial ink or paints on...
29. ### Depletion zone and current in forward-biased PN junction

Hello. I've learned that in PN junction, forward-biasing on it pushes holes in P-type and electrons in N-type toward the junction so depletion width is reduced. Is it due to that in N-type side(P-type side), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And...
30. ### Depletion zone and current in forward-biased PN junction

Hello. I've learned that in PN junction, forward-biasing pushes holes in P-type and electrons in N-type forward junctions so depletion width is reduced. Is it due to that in N-type (P-type), pushed electrons (holes) are recombined with holes (electrons) in depletion zone? And what is true...