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In generic resistive-pulse sensing, two electrolyte reservoirs are connected through a small aperture. Electrodes apply a bias and a low-noise current amplifier records the pore current. Passage of a weakly charged insulating particle excludes conducting liquid, usually increasing resistance and giving a transient current decrease at fixed voltage. Pulse amplitude, duration and event rate contain size-, transport- and concentration-dependent information, subject to calibration.

Advantages include label-free single-particle counting, electrical readout and small active volume. Limitations include clogging, electrode/pore noise, finite bandwidth, uncertain particle trajectories and surface-conduction effects; a pulse is not intrinsically chemically specific. Strong particle charge or concentration polarization can complicate, or even reverse, the simple blockade signal. The schematic below uses only generic nonbiological particle transport.

The same current flows through both resistances, $I=V_{\mathrm{oc}}/(R+R_L)$. The load terminal voltage is $I{R}_L$, smaller than the open-circuit voltage. The electrical battery symbol represents the maintained thermoelectric source under this model; heat input is still required.

Above-gap photon absorption generates electrons and electron holes. A p-n junction's built-in field and carrier diffusion direct them toward selective contacts; their nonequilibrium populations can maintain separated quasi-Fermi levels and deliver electrical power. The equilibrium built-in voltage alone is not a battery supplying continuous power.

Choose diode current positive into the cell. An idealized characteristic isIllumination shifts the curve downward. At short circuit $I(0)=-I_{\mathrm{sc}}$; at open circuit $I(V_{\mathrm{oc}})=0$. Between those points, $V>0$ and $I<0$, so the delivered power $P=-VI$ is positive.

The solar-cell fill factor compares maximum delivered power with the open/short-circuit rectangle:Series resistance, leakage, recombination and temperature change the shape and hence the fill factor. Neither the short-circuit nor the open-circuit point itself delivers power.

The useful bandgap depends on the illumination spectrum, not only on whether the device is indoors or outdoors. The stipulated $1.45\mathrm{eV}$ gap gives a long-wavelength absorption threshold near $855\mathrm{nm}$; $1.7\mathrm{eV}$ gives about $729\mathrm{nm}$ using ${\lambda }_g\simeq 1240/E_g$ in nanometers.

Outdoor sunlight contains substantial visible and near-infrared power, so cadmium telluride can use a broader portion of that spectrum while retaining a useful output voltage. Its direct-gap absorption permits thin absorbers and large-area thin-film manufacture. Challenges include contacts and interfaces, collection and recombination, material supply and managing cadmium-containing material through fabrication and end-of-life handling.

Many indoor lamps concentrate their emission in the visible and provide little near-infrared power. A wider-gap absorber can then trade fewer lost useful photons for a higher attainable voltage and a smaller thermal dark-current penalty. Hydrogenated amorphous silicon has strong visible absorption, permits low-temperature large-area deposition and can suit low-power indoor devices. Disorder and defects restrict transport, and light-induced degradation and passivation stability must be controlled. Its larger gap forfeits more of the outdoor red/near-infrared spectrum.

These are suitability arguments, not guaranteed efficiencies. Indoor lamp spectra differ, and shunt leakage and recombination become particularly important at low light. Bandgap alone does not establish which finished device produces more power in every room.

For a monolithic series-connected multi-junction solar cell, all junctions carry the same terminal current, so a weakly illuminated junction limits the useful series current. Adjust absorber thicknesses, compositions and optical coupling to balance collected photocurrent. Tunnel interconnects provide electrical continuity; low-loss contacts and interfaces also matter. Equal incident energy in each spectral band would not guarantee equal current, because photon counts and collection efficiencies differ.

Put the largest bandgap at the illuminated top and the smallest at the bottom:The top absorber captures high-energy photons while transmitting lower-energy photons to the subsequent layers. Placing germanium first would absorb photons that the higher-gap cells could use at higher voltage.

The absorption edges are approximatelyFor ideal sharp, complete absorption without reflection, the available plotted spectral bands are therefore the visible region below $660\mathrm{nm}$ for the top cell, $660$–$886\mathrm{nm}$ for the middle cell, and $886$–$1850\mathrm{nm}$ for germanium. Photons beyond $1850\mathrm{nm}$ pass all three ideal absorbers. The source plot begins around $350\mathrm{nm}$, so it does not supply an ultraviolet integral below that point.

Using coarse readings of the provided curve, the band integrals are of order $1.2\times 10^4$, $0.7\times 10^4$ and $1.2\times 10^4$ in plotted-ordinate-units times nanometers, respectively. These are only approximate areas under a low-resolution graph, not calibrated radiances in SI units: the ordinate gives no physical unit or spectral normalization. The robust result is the band allocation; precise photocurrent matching needs a calibrated spectrum and each junction's external quantum efficiency,Thus the diagram and band boundaries establish the intended stack, while the plot cannot justify precise watt-per-area or current values.

Conductive atomic force microscopy can map current near the pits while recording topography. Use a conducting tip, a suitable counter-contact to the film and an imposed bias, then compare current maps and local current–voltage curves near and away from dislocations. Spreading resistance microscopy is another useful electrical mode when its contact conditions and calibration are suitable.

Current depends on tip contact area, contact resistance, surface oxide, bias and local carrier barriers as well as the material's conductivity. Compare regions under controlled force and bias, check repeated scans for damage and distinguish a geometrical contact artifact from an electrical change. A surface-potential image can complement these measurements, but it does not by itself measure conductivity.

Use Kelvin probe force microscopy to quantify a local contact-potential difference. A conducting tip and sample form a position-dependent capacitor. Apply a voltage with adjustable direct and small alternating components,The electrostatic force is proportional to $C^{\prime }(z)V(t{)}^2/2$, so its component at $\omega$ is proportional toup to the chosen force-direction convention. A lock-in amplifier detects this component and a second controller adjusts $V_{\mathrm{dc}}$ to null it. At the null, $V_{\mathrm{dc}}=V_{\mathrm{CPD}}$. The compensation voltage becomes the potential image.^[ref]

A lift pass can reduce direct topographic interactions. Calibration on a reference with a known work function is required for an absolute work-function interpretation, and the sign convention must state which electrode is biased. On a semiconductor the result can include surface band bending, trapped charge and surface chemistry, so it need not equal a simple map of bulk electrochemical potential.

The measured potential is a spatially weighted electrostatic signal, not an infinitesimal-point voltage. The apex, cone and cantilever all contribute capacitance; increasing lift height weakens the signal and broadens its lateral averaging. Small pits can consequently show reduced or distorted contrast.

Imperfect topographic tracking changes the true separation on the lift pass, producing crosstalk correlated with pit geometry. Tip contamination or work-function drift changes the reference. Adsorbed water, mobile charges, illumination, atmosphere and surface states can change the specimen during measurement; semiconductor band bending can also depend on the applied electrical excitation.

There is a tradeoff between small lift height and suppressing short-range/topographic interference. Repeat at several heights, check trace/retrace and an electrical reference, and compare with independently measured electrical response. A stable potential contrast is evidence of a local electrostatic difference, not by itself proof of a particular dislocation's conductivity.

A spin valve contains a magnetically soft free ferromagnet, a thin nonmagnetic metallic spacer and a reference ferromagnet pinned by exchange bias from an antiferromagnet. The recording track's stray field rotates or reverses the free-layer moment while the reference remains approximately fixed. Spin-dependent scattering makes the resistance lower for parallel moments and higher for antiparallel moments. A sense current converts this into a voltage signal, or a fixed voltage into a current signal.

A useful angular approximation is $R(\theta )=R_P+(R_{AP}-R_P)(1-\cos \theta )/2$. Biasing the equilibrium moments near $90^{\circ }$ gives an approximately linear response to small track fields. Pinning stability, magnetic shielding and the sensor's spatial extent matter for reading adjacent narrow bits.^[ref]

The arrangement is diode sputter deposition: the Au target, a, is attached to the upper cathode assembly c; positive Ar ions bombard it and sputter Au onto the wafer. The lower wafer-holder electrode b is the anode in the simple two-electrode arrangement shown.

Unlike evaporation, sputtering needs enough inert gas to sustain a discharge. Over a low-pressure operating interval, raising Ar pressure can increase ionization and ion current and hence the sputtering rate at comparable applied voltage. This is not a universal monotonic law: at higher pressure, scattering and thermalization of sputtered Au reduce the fraction reaching the wafer; at fixed regulated power, target voltage and current also adjust. A pressure increase can initially increase the rate, but excessive pressure lowers transport efficiency.

The stored energy is $0.75(7)=5.25\mathrm{Wh}$, and the load draws $P=IV=(20\times 10^{-6})(2.5)=50\mu \mathrm{W}$. HenceThis is an ideal energy-budget estimate using 365.25 days per year. It assumes the stated energy is usable at this load, constant current and voltage, and negligible self-discharge, ageing and reserve capacity. No biological operating model is required.

The discharge reaction is $2\mathrm{Li}+{\mathrm{I}}_2\to 2\mathrm{LiI}$. It transfers two electrons and has $\Delta G^{\circ }=-539.4\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ per reaction as written. The reversible open-circuit voltage isThe supplied free energy is already at approximately the requested temperature, so an additional temperature factor is unnecessary. Actual activities or discharge polarization could alter the terminal voltage.

The Seebeck effect produces an open-circuit voltage when a material has a temperature gradient: $S=-dV/dT$ for the stated sign convention. A circuit containing dissimilar thermoelectric legs converts this into useful voltage and current. The intrinsic thermoelectric figure of merit isHere $\sigma$ is electrical conductivity and $\kappa ={\kappa }_e+{\kappa }_L$ total thermal conductivity. $Z$ has units ${\mathrm{K}}^{-1}$; $ZT$ is dimensionless. A large Seebeck coefficient and electrical conductivity, together with low thermal conductivity, favour efficient conversion.

A lead-acid battery is suitable. Its positive electrode reduces PbO2 to PbSO4 and its negative electrode oxidizes Pb to PbSO4. The net discharge reaction isUsing the supplied rounded potentials gives $E^{\circ }=1.70-(-0.35)=2.05\mathrm{V}$. The Nernst equation, taking solid and water activities as unity, givesAt $\mathrm{pH}=1$ and $298\mathrm{K}$,Thus $1.93\mathrm{V}$ if sulfate activity is assumed unity. The pH alone does not specify sulfate activity, particularly where bisulfate formation and nonideal concentrated acid matter; without that assumption the numerical voltage is underdetermined.

For recharge, reverse both electrode reactions without irreversible loss of active material. Use porous, electronically connected Pb and PbO2 on acid-compatible conducting grids, with enough pore volume for PbSO4 formation and electrolyte transport. Fine, reversible sulfate deposits are desirable; coarse persistent crystals cause sulfation. The separator must remain acid-resistant, electronically insulating and permeable to electrolyte ions while preventing shorts; selective ion exchange is not intrinsically required. A compatible lead-alloy grid is preferable to assuming any metallic substrate survives the positive electrode's oxidizing acidic environment. Control current and charging voltage to limit hydrogen evolution, oxygen evolution, water loss, corrosion, heating and active-material shedding. Nickel hydroxide-based alkaline electrodes are poor choices in this acidic electrolyte because their phase stability and reaction conditions differ from those of their tabulated alkaline half-reactions.

Two electrons are transferred per formula unit of Li2O2. Its theoretical specific capacity isAt $3\mathrm{V}$, the corresponding theoretical specific energy is $3q=3.50\mathrm{Wh}{\mathrm{g}}^{-1}$, or $3500\mathrm{Wh}\mathrm{k}{\mathrm{g}}^{-1}$. The mass basis is Li2O2, equivalently the combined stoichiometric masses of consumed Li and O2; a value normalized to Li metal alone would be different.

A real lithium-air battery also includes electrolyte, porous positive-electrode support, separator, current collectors, excess reactants, packaging and possibly oxygen treatment. Insulating Li2O2 can block pores and electron transport, limiting utilization; polarization, electrolyte decomposition, moisture/CO2 contamination and parasitic reactions lower useful voltage and reversible capacity. A lithium-ion battery instead shuttles Li ions between pre-existing host electrodes, generally in a closed cell without consuming atmospheric oxygen; the oxygen/peroxide reaction and its mass/transport requirements make the Li-air mechanism distinct.

The Shockley-Queisser limit is the detailed-balance efficiency bound for an ideal single-junction solar cell with radiative recombination under specified illumination and optical conditions. Below-gap photons are not absorbed and excess energy of above-gap photons is thermalized; radiative emission further limits the output voltage. The often quoted unconcentrated terrestrial maximum is roughly one third, not an illumination-independent universal percentage.

A multi-junction solar cell places a high-gap junction before lower-gap junctions, dividing the spectrum so photons generate carriers in a better-matched absorber. This reduces transmission and thermalization losses and can exceed the single-junction bound without violating its assumptions: there is now more than one junction. In a two-terminal series stack, all junctions carry the same current, so the lowest photocurrent limits the whole device. Current matching uses bandgap choice, absorber thickness, optical management and sometimes lateral area to make the generated currents comparable for the intended spectrum. Independently contacted junctions need not share the same current.^[ref]

A MOSFET is a voltage-controlled three-terminal switch: the insulated gate controls a conductive channel, giving high input impedance and useful current gain at the circuit level. A CMOS inverter actively restores either logic rail, has voltage gain near its switching threshold, and ideally draws no static supply current in either settled logic state. Real devices have leakage and consume energy while switching.

A single p-n junction is a two-terminal diode; its current is controlled by its own terminal voltage, so it does not by itself provide an independently controlled switch, gain and restoring inversion. Cross-coupled CMOS inverters form a bistable memory element. A lone inverter is not itself a complete memory cell, and a p-n junction can still serve useful rectification or capacitance functions.

Use a lithium-metal negative electrode and a carbon-monofluoride composite positive electrode, separated by a porous, electrically insulating battery separator wetted by a lithium-salt electrolyte in a suitable nonaqueous solvent. Conducting carbon and a binder provide electronic contact through the fluorinated-carbon electrode to its electric current collector; the lithium electrode has its own electric current collector. A sealed stacked or wound assembly supplies useful area and contains the electrolyte.

During discharge lithium is the anode and the carbon-monofluoride composite is the cathode. lithium ions move through the electrolyte while electrons flow through the external load. The battery separator prevents electronic shorting while permitting ionic transport. An aqueous electrolyte is unsuitable because metallic lithium reacts with water. The requested very long operating time requires enough active material and low self-discharge, not merely a high nominal voltage.

Using $365$ days per year, the required time is $2\times 365\times 24=17520\mathrm{h}$. Hencelithium transfers one electron per atom, soThis is the stoichiometric minimum for one cell, or one cell-equivalent parallel assembly, with complete utilization and no self-discharge. Practical loading must be larger. If a pack uses several cells in series, each series cell must carry the full delivered charge and the total lithium mass increases accordingly; no required pack voltage or series count is supplied.

For the $x=1$ reaction there is one mole of transferred electrons per mole of reaction. Treating the supplied fresh-cell open-circuit voltage as the standard equilibrium cell potential givesA fresh-cell voltage alone would not normally establish standard conditions or equilibrium. The result above is the formal standard-free-energy estimate under the interpretation required to use the given datum; a metastable open-circuit voltage should not be mistaken for an independently measured standard thermodynamic potential.