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14

The physical 'meaning' of the imaginary part of the impedance is that it represents the energy storage part of the circuit element. To see this, let the sinusoidal current $i = I\cos(\omega t)$ be the current through a series RL circuit. The voltage across the combination is $$v = Ri + L\frac{di}{dt} = RI\cos(\omega t) - \omega LI\sin(\omega t)$$ The ...


5

There is a physical meaning behind the imaginary component of the impedance. You can re-cast the complex impedance $Z = R + jX$ (using engineering's notation $j$ for the imaginary unit) in polar form to get $Z = |Z|\exp(j\phi)$. $|Z|$ is the magnitude of the impedance, and scales the amplitude of the current to get the amptlitude of the voltage. $\phi = ...


5

The key difference between a Zener diode and a normal diode is that the Zener diode has a low breakdown voltage - typically in the few volts range. The breakdown voltage is low because the heavy doping means the depletion layer is very thin, and even at a low voltage the field strength over this thin depletion layer is very high. With a conventional diode ...


4

… an ideal power source capable of providing infinite current with no drop in the voltage it supplies. … Let's ignore the effects of current density on superconductors for now. … In these phrases is the explanation for the contradictory possibilities you have computed: you have supposed an impossible circuit. As a mathematical model, the behavior of ...


4

From "The Transistor, A Semi-Conductor Triode", by J. Bardeen and W. H. Brattain, Phys Rev. 74(2), 230-231 (1948): "The device consists of three electrodes placed on a block of germanium as shown schematically in Fig. 1. Two, called the emitter and collector, are of the point-contact rectifier type and are placed in close proximity (separation ~0.005 to ...


3

As Kevin Reid aptly explains, the circuit you have drawn is not realizable. But, let's take the closest physical thing you could build, assuming: your voltage source can supply enough energy that we don't hit its limits like all physical things, this apparatus has non-zero size Then, the circuit you actually built is this: simulate this circuit ...


3

The electrons need to get from the top to the bottom without any interference from any gas molecules that might be in the channels. If nothing else, collisions with gas molecules will degrade performance. At atmospheric pressure, I don't think the device would work at all. You can blow a hole through an MCP with over-voltage, but I'm not sure how this ...


3

Calling it a built-in voltage is something of a misnomer. People usually think of "voltage" as "what you measure with a voltmeter". So "voltage" is normally synonymous with "electrochemical potential of electrons" (in stat mech terminology) and with "difference in fermi level" (in semiconductor terminology). Under this definition, the built-in "voltage" is ...


2

The light output of a LED is pretty linear with the current through it, over its normal operating range. Light does usually drop off from linear with current at the high end. Sometimes that high end is not included in the normal operating range, so the graph you see in the datasheet will be linear. Common T1-3/4 20 mA indicator LEDs are usually linear ...


2

First of all note, that ions do not move in the semiconductor. Only electrons and holes move there. The depletion results from diffusion of the free electrons from the n-region into the p-region and the diffusion of holes from the p-region into the n-region. In either case it is a thermodynamical process. The electrons form something like a dense gas in ...


2

The analogies may be built in various ways – similar simple mathematical relationships like $U=RI$ are among many of them – but I would choose the analogy consistent with the Czech language where "napětí" [nuh-pyeh-tyea] means both "voltage" and "tension". I guess that even English speakers must sometimes say "electric tension" instead of "voltage". In the ...


2

Is it possible to produce gamma radiaton using radio emitter? Unlikely. A 'radio emitter' consists of, at least, some type of antenna and a transmitter to drive that antenna. The size of the antenna is related to the wavelength of the transmitted radio wave, e.g., half-wave dipole, quarter-wave monopole. But the wavelength of gamma rays is less than ...


2

One form of evidence is the ionization energies of silicon. Nth ionization energy is the energy needed to remove the nth electron. There is a big jump going from the 4th ionization energy (~4000 kJ/mol) to the 5th ionization energy (~16000 kJ/mol). Another form of evidence is the compounds silicon makes. Silicon forms $\mathrm{SiH}_4$, $\mathrm{SiF}_4$, ...


1

Early, while the periodic table of the elements was explored by Mendeleev, it was already known that it can have nearly always 4 bonding. The source of this knowledge was at this time the analysis of the mass ratios of its compounds. Later, after the Bohr model was developed, in the times of the modern quantum chemistry it is interpreted as it has 4 valency ...


1

Another interesting analogy, pointed out by Prof. Graeme Milton, can be seen when you examine Maxwell's equations in media at a fixed frequency $\omega$: $$ \boldsymbol{\nabla} \times \mathbf{E} = i\omega\boldsymbol{\mu}(\mathbf{x})\cdot\mathbf{H}(\mathbf{x}) ~;~~ \boldsymbol{\nabla} \times \mathbf{H} = ...


1

Imaginary components in physics often mean phase shifts. In this case the impedance is sort of like a resistance, but it kicks in when there's a changing current by messing with its phase.


1

In this case, the magnitude is telling you how to scale your input signal, and the argument is telling you how to phase shift it. Complex numbers usually represent 'amplification' and 'twist'. So, say, 1 means 'leave it the same', 2 means 'double it', 0.5 means 'halve it', i means 'one quarter turn', -1 means 'one half turn', -3i means 'triple it and give ...


1

Radios work with a form of radiation called non-ionizing radiation. This means the EM waves contain enough energy to move the atoms (charges) around but not enough energy to break particles loose. Ionizing radiation removes particles because they carry a lot more energy and can break atomic bonds. These travel as UV-rays, x-rays or gamma-rays. In ...


1

As I recall some models of Samsung phones display the same message but many phones don't. My Nexus 5 does not and my LG tablet does not. Modern phones use lithium batteries. It is important that these are not overcharged because this degrades the batteries by forming deposits of metallic lithium. However all modern phones will automatically stop charging as ...


1

I am not an expert in thermodynamics but I think the following is reasonable: When heat flows from A to B (temperature $T_a$ and $T_b$) then you could theoretically do work - efficiency given by the ratio of temperatures. A Peltier is an inefficient heat engine running in reverse (a heat pump), and I thought the efficiency is the ratio between the work ...


1

You may be aware that both torque and angular momentum can be represented as a vector - and that such vectors follow the normal rules of vector addition. Thus, if you have equal rotation about both the X and the Y axis, what you really have is rotation about the XY axis; and in general, rotation about an arbitrary axis can be projected onto the X, Y and Z ...


1

As radio amateurs we've all learned the various relationships of power, voltage, current and resistance as expressed in Ohm's Law Ohm's law is: $$ E = IR \tag{1} $$ This doesn't directly say anything about power. There is the related Joule's first law, which relates to electrical power converted to heat in resistive materials: $$ P = I^2 R \tag{2} $$ ...


1

There are a few factors that govern laser diode turn-on time. The first is the junction capacitance, which is the same thing that causes turn-on delay in an ordinary junction diode. Under forward bias, the capacitance is proportional to the current and the diode transit time, just as with any pn-junction diode. The second is unique to laser diodes. ...


1

Optical systems not involving magnetic fields are symmetric. So, if the display passes light in one direction, it will pass light in the other. Putting a mirror at the back of the TFT and lighting it from the front is therefore equivalent, expect that some light will be attenuated on the way in as pointed out by @CarlWitthoft in the comments. As a ...


1

In the first chapter of Sze's classic Physics of Semiconductor Devices, one can find: (1) in low electric fields, the drift velocity of carriers is proportional to the electric field strength (section 1.5 in the 2nd edition). It then gives a number of approximations, depending on the primary scattering mechanism. (2) in high field regions, nonlinearities ...


1

Even if the floating Al film is (nearly) disconnected in DC, it is still capacitively coupled to the substrate. Since Kelvin probe techniques use capacitance modulation, the behaviour of the experiment will be more or less identical to the case of a connected film, since tip-film capacitance is so tiny compared to the film-substrate capacitance. It's ...


1

Earth's zero potential is just an arbitrary point similar to (0,0) of co-ordinate system. It has been chosen for Engineering practices because it has very very low theoretical potential (in light with charge at Infinity) and it's easily accessible to everyone and adding charge to it doesn't change it's theoretical potential. With reference to this arbitrary ...


1

The voltage across a capacitor cannot change when there is no current, so if there is no current, as the input voltage rises, the output voltage also rises. There is no current (or almost no current) when the voltage across that diode is positive. According to Wikipedia there are better ways to make voltage doublers.


1

The main solution is to give up Silicon altogether since it is very inefficient, compared to some of the compound semiconductors(such as GaAs). However, GaAs will eventually reach the same limitations. In any case, you can't really make a transistor from half an atom, therefore there are some physical limits as to how small you can make a transistor and ...



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