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Piezoelectric crystals: certain materials tend to generate voltages in response to mechanical strain, and vice versa - contract or expand in response to applied fields or the currents flowing through them; in some settings, this action may in turn affect the applied voltage or admitted current, resulting in oscillating action. Simple actuators - electromagnets, speakers, solenoids, relays: as noted previously, electric currents flowing through properly oriented wires can induce strong, coherent magnetic fields; these magnetic fields may, in turn, interact with materials where electron spins are coherently aligned: permanent magnets and ferromagnetic / paramagnetic metals. Antenna gains of 10 are common, so the electric bill is not what the ERP suggests. Because gates are not expected to directly drive significant loads (several milliamps is usually the limit), CMOS transistors are selected so that their resistances and voltage response characteristics eliminate the risk of short-circuit damage when input voltage is somewhere between ground and Vcc; that said, output voltage levels and other gate characteristics are guaranteed to be sane only within certain specific ranges of "0" and "1" inputs. Switches: one of the most rudimentary electromechanical devices, switches interrupt and close circuits in response to an externally applied force.

A striking demonstration of this is connecting the terminals of two similar, brushed DC motors together: rotating one of them will induce a voltage sufficient to turn the other. The circuit consists of two identical MOSFET switches driving small resistive loads equipped with an output tap; this tap will be at Vsupply when the MOSFET is off, and close to 0V when fully conducting. On printed circuit boards, miniature surface-mount ferrite beads can be used to protect analog circuitry from digital noise, or to reduce radio interference. 0.02 a piece), rather than cherry-pick more expensive ones for every individual circuit. The actual power rules are more complicated than this table, and stations can argue for and get a higher limit. They are used to dampen and filter out high-frequency current spikes. I²R) will also be negligible - around 1/8 watt; for higher currents, the amount of dissipated heat goes through the roof pretty quickly, though - and therefore, resistor-based current limiters are useful only in low-power uses. This can be achieved by driving the coils directly with alternating sine wave currents (synchronous motors), by providing carefully timed voltage pulses (brushless and stepper motors), or with steady direct currents, mechanically switched by commutators (brushed motors).

Resistors with low values (100Ω or so) usually perform as expected to 500 MHz or so; that said, large resistors - such as 1 MΩ - exist to admit only tiny currents, so their performance is easily thrown off by even fairly minutiae parasitic effects. Standard ("preferred") values are selected to make most sense given the expected tolerances, with E6 scale being used most commonly. Common inductor values in electronic circuits range from 1 µH to 470 mH or so. Another common use is galvanically isolating circuits for safety reasons - i.e., only magnetic coupling, but no direct charge flow pathways, would be maintained. It does, however, need bipolar switching: if you simply apply a positive voltage to the gate, and then disconnect it - the gate-source "capacitor" will stay charged, and the transistor will continue conducting for a longer while (dependent on humidity, handling, etc); even after this charge disappears, a new one can be easily accumulated due to further handling, parasitic coupling, and so forth. First, we need to find an equivalent resistor that, when placed across the terminals of our 9V battery, would conduct just 20 mA. Electrolytic capacitors enjoy some of the highest capacitances in proportion to their cost and size - but need to be polarized, work well only for fairly low voltages, have some leakage current, and tend to exhibit non-trivial resistance (denoted as ESR, and limiting their ability to deal with high-frequency signals); so avoiding electrolytics as long as possible is generally a good idea (cheap multi-layer ceramic capacitors - MLCC - are available up to at least 10 µF).

Standard ceramic capacitors usually perform as expected to around 100 MHz; past that point, parasitic inductance tends to take hold and makes them perform far worse than expected. The capacitor will never charge past the voltage across the terminals of the lightbulb (which can be calculated from the lightbulb's resistance, as per Ohm's law) - and will discharge through it when SW1 is opened. Antenna amplifiers - Many people think adding an amplifier to their antenna will improve the performance of the antenna. It can save space with almost no drop in performance. Transformers: constructed by pairing two inductors, typically wrapped around a common ferromagnetic core that guides and contains the electromagnetic field to improve performance. Sometimes, windings may have multiple taps, or additional windings can be provided as a feedback mechanism for building high voltage flyback transformers that exploit resonant frequencies of the ferrite core. Incandescent lamps: simple, well-known components that exploit the heat-driven light emission of a resistive metal wire placed under vacuum or in a low-pressure, inert gas (to prevent oxidation and minimize convection-based heat transfer).

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