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83-420: The Solar Wind Spectrometer (SWS) experiment aimed to provide the ability "to measure energies, densities, incidence angles and temporal variations of the solar wind plasma that strikes the surface of the moon". The experiment instrument consist of seven Faraday cups , that measure the amount of charged particles. One central cup points perpendicularly to the surface. The other six cups are angled at 30 degrees from

166-430: A galvanometer , but this method involves breaking the electrical circuit , which is sometimes inconvenient. Current can also be measured without breaking the circuit by detecting the magnetic field associated with the current. Devices, at the circuit level, use various techniques to measure current: Joule heating, also known as ohmic heating and resistive heating , is the process of power dissipation by which

249-453: A rectifier . Direct current may flow in a conductor such as a wire, but can also flow through semiconductors , insulators , or even through a vacuum as in electron or ion beams . An old name for direct current was galvanic current . Natural observable examples of electric current include lightning , static electric discharge , and the solar wind , the source of the polar auroras . Man-made occurrences of electric current include

332-411: A circuit, as an equal flow of negative charges in the opposite direction. Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers . Negatively charged carriers, such as the electrons (the charge carriers in metal wires and many other electronic circuit components), therefore flow in

415-405: A common lead-acid electrochemical cell, electric currents are composed of positive hydronium ions flowing in one direction, and negative sulfate ions flowing in the other. Electric currents in sparks or plasma are flows of electrons as well as positive and negative ions. In ice and in certain solid electrolytes, the electric current is entirely composed of flowing ions. In a metal , some of

498-416: A definition of current independent of the type of charge carriers, conventional current is defined as moving in the same direction as the positive charge flow. So, in metals where the charge carriers (electrons) are negative, conventional current is in the opposite direction to the overall electron movement. In conductors where the charge carriers are positive, conventional current is in the same direction as

581-434: A fast secondary electron. Current (electricity) An electric current is a flow of charged particles , such as electrons or ions , moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge carriers , which may be one of several types of particles, depending on the conductor . In electric circuits

664-413: A grounded cylindrical shield – 3 having an axial round hole coinciding with the hole in the electron-suppressor lid – 2. The electron-suppressor lid is connected by 50 Ω RF cable with the source B e s {\displaystyle B_{es}} of variable DC voltage U e s {\displaystyle U_{es}} . The receiver-cup is connected by 50 Ω RF cable through

747-447: A localized high current. These regions may be initiated by field electron emission , but are then sustained by localized thermionic emission once a vacuum arc forms. These small electron-emitting regions can form quite rapidly, even explosively, on a metal surface subjected to a high electrical field. Vacuum tubes and sprytrons are some of the electronic switching and amplifying devices based on vacuum conductivity. Superconductivity

830-428: A metal wire is connected across the two terminals of a DC voltage source such as a battery , the source places an electric field across the conductor. The moment contact is made, the free electrons of the conductor are forced to drift toward the positive terminal under the influence of this field. The free electrons are therefore the charge carrier in a typical solid conductor. For a steady flow of charge through

913-450: A metallic cylindrical receiver-cup – 1 (Fig. 1) closed with, and insulated from, a washer-type metallic electron-suppressor lid – 2 provided with the round axial through enter-hollow of an aperture with a surface area S F = π D F 2 / 4 {\displaystyle S_{F}=\pi D_{F}^{2}/4} . Both the receiver cup and the electron-suppressor lid are enveloped in, and insulated from,

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996-404: A millimetre per second. To take a different example, in the near-vacuum inside a cathode-ray tube , the electrons travel in near-straight lines at about a tenth of the speed of light . Any accelerating electric charge, and therefore any changing electric current, gives rise to an electromagnetic wave that propagates at very high speed outside the surface of the conductor. This speed is usually

1079-408: A particular band called the valence band . Semiconductors and insulators are distinguished from metals because the valence band in any given metal is nearly filled with electrons under usual operating conditions, while very few (semiconductor) or virtually none (insulator) of them are available in the conduction band , the band immediately above the valence band. The ease of exciting electrons in

1162-422: A result of the vaporisation of 1100 kg of plastic materials contained with the rocket stage. The shockwave was estimated to have travelled 140 km at a speed of 2 km/s. Faraday cup A Faraday cup is a metal (conductive) cup designed to catch charged particles . The resulting current can be measured and used to determine the number of ions or electrons hitting the cup. The Faraday cup

1245-472: A significant fraction of the speed of light, as can be deduced from Maxwell's equations , and is therefore many times faster than the drift velocity of the electrons. For example, in AC power lines , the waves of electromagnetic energy propagate through the space between the wires, moving from a source to a distant load , even though the electrons in the wires only move back and forth over a tiny distance. The ratio of

1328-405: A surface, the current I (in amperes) can be calculated with the following equation: I = Q t , {\displaystyle I={Q \over t}\,,} where Q is the electric charge transferred through the surface over a time t . If Q and t are measured in coulombs and seconds respectively, I is in amperes. More generally, electric current can be represented as

1411-599: Is I , which originates from the French phrase intensité du courant , (current intensity). Current intensity is often referred to simply as current . The I symbol was used by André-Marie Ampère , after whom the unit of electric current is named, in formulating Ampère's force law (1820). The notation travelled from France to Great Britain, where it became standard, although at least one journal did not change from using C to I until 1896. The conventional direction of current, also known as conventional current ,

1494-514: Is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature . It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden . Like ferromagnetism and atomic spectral lines , superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect ,

1577-655: Is an SI base unit and electric current is a base quantity in the International System of Quantities (ISQ). Electric current is also known as amperage and is measured using a device called an ammeter . Electric currents create magnetic fields , which are used in motors, generators, inductors , and transformers . In ordinary conductors, they cause Joule heating , which creates light in incandescent light bulbs . Time-varying currents emit electromagnetic waves , which are used in telecommunications to broadcast information. The conventional symbol for current

1660-450: Is an invariable constant for each measurement. Therefore, the average velocity ⟨ v i ⟩ {\displaystyle \langle v_{i}\rangle } of ions arriving into the Faraday cup and their average energy ⟨ E i ⟩ {\displaystyle \langle {\mathcal {E}}_{i}\rangle } can be calculated (under

1743-411: Is arbitrarily defined as the direction in which positive charges flow. In a conductive material , the moving charged particles that constitute the electric current are called charge carriers . In metals, which make up the wires and other conductors in most electrical circuits , the positively charged atomic nuclei of the atoms are held in a fixed position, and the negatively charged electrons are

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1826-683: Is current. Magnetic fields can also be used to make electric currents. When a changing magnetic field is applied to a conductor, an electromotive force (EMF) is induced, which starts an electric current, when there is a suitable path. When an electric current flows in a suitably shaped conductor at radio frequencies , radio waves can be generated. These travel at the speed of light and can cause electric currents in distant conductors. In metallic solids, electric charge flows by means of electrons , from lower to higher electrical potential . In other media, any stream of charged objects (ions, for example) may constitute an electric current. To provide

1909-484: Is defined from the equation M i v i , s 2 / 2 = e Z i U g {\displaystyle M_{i}v_{i,s}^{2}/2=eZ_{i}U_{g}} where v i , s {\displaystyle v_{i,s}} is the velocity of the ion stopped by the decelerating potential U g {\displaystyle U_{g}} , and M i {\displaystyle M_{i}}

1992-433: Is impacted by two error sources: 1) the emission of low-energy secondary electrons from the surface struck by the incident charge and 2) backscattering (~180 degree scattering) of the incident particle, which causes it to leave the collecting surface, at least temporarily. Especially with electrons, it is fundamentally impossible to distinguish between a fresh new incident electron and one that has been backscattered or even

2075-423: Is in a nanowire , for every energy there is a state with electrons flowing in one direction and another state with the electrons flowing in the other. For a net current to flow, more states for one direction than for the other direction must be occupied. For this to occur, energy is required, as in the semiconductor the next higher states lie above the band gap. Often this is stated as: full bands do not contribute to

2158-468: Is low, gases are dielectrics or insulators . However, once the applied electric field approaches the breakdown value, free electrons become sufficiently accelerated by the electric field to create additional free electrons by colliding, and ionizing , neutral gas atoms or molecules in a process called avalanche breakdown . The breakdown process forms a plasma that contains enough mobile electrons and positive ions to make it an electrical conductor. In

2241-455: Is opposite that of the chosen reference direction. Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance , one arrives at the usual mathematical equation that describes this relationship: I = V R , {\displaystyle I={\frac {V}{R}},} where I

2324-655: Is opposite to the velocity of the charges. In SI units , current density (symbol: j) is expressed in the SI base units of amperes per square metre. In linear materials such as metals, and under low frequencies, the current density across the conductor surface is uniform. In such conditions, Ohm's law states that the current is directly proportional to the potential difference between two ends (across) of that metal (ideal) resistor (or other ohmic device ): I = V R , {\displaystyle I={V \over R}\,,} where I {\displaystyle I}

2407-469: Is the Faraday cup I-V characteristic which can be observed and memorized by oscilloscope In Fig. 1: 1 – cup-receiver, metal (stainless steel). 2 – electron-suppressor lid, metal (stainless steel). 3 – grounded shield, metal (stainless steel). 4 – insulator (teflon, ceramic). C F {\displaystyle C_{F}} – capacity of Faraday cup. R F {\displaystyle R_{F}} – load resistor. Thus we measure

2490-433: Is the current through the conductor in units of amperes , V is the potential difference measured across the conductor in units of volts , and R is the resistance of the conductor in units of ohms . More specifically, Ohm's law states that the R in this relation is constant, independent of the current. In alternating current (AC) systems, the movement of electric charge periodically reverses direction. AC

2573-400: Is the current, measured in amperes; V {\displaystyle V} is the potential difference , measured in volts ; and R {\displaystyle R} is the resistance , measured in ohms . For alternating currents , especially at higher frequencies, skin effect causes the current to spread unevenly across the conductor cross-section, with higher density near

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2656-441: Is the form of electric power most commonly delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave , though certain applications use alternative waveforms, such as triangular or square waves . Audio and radio signals carried on electrical wires are also examples of alternating current. An important goal in these applications is recovery of information encoded (or modulated ) onto

2739-405: Is the ion charge state, and f ( v ) {\displaystyle f(v)} is the one-dimensional ion velocity distribution function. Therefore, the ion current at the ion-decelerating voltage U g {\displaystyle U_{g}} of the Faraday cup can be calculated by integrating Eq. ( 2 ) after substituting Eq. ( 3 ), where the lower integration limit

2822-485: Is the ion mass. Thus Eq. ( 4 ) represents the I-V characteristic of the Faraday cup. Differentiating Eq. ( 4 ) with respect to U g {\displaystyle U_{g}} , one can obtain the relation where the value − n i S F ( e Z i / M i ) = C i {\displaystyle -n_{i}S_{F}(eZ_{i}/M_{i})=C_{i}}

2905-456: Is the rate at which charge passes through a chosen unit area. It is defined as a vector whose magnitude is the current per unit cross-sectional area. As discussed in Reference direction , the direction is arbitrary. Conventionally, if the moving charges are positive, then the current density has the same sign as the velocity of the charges. For negative charges, the sign of the current density

2988-403: Is zero net current within the metal. At room temperature, the average speed of these random motions is 10 metres per second. Given a surface through which a metal wire passes, electrons move in both directions across the surface at an equal rate. As George Gamow wrote in his popular science book, One, Two, Three...Infinity (1947), "The metallic substances differ from all other materials by

3071-519: The Inductively coupled plasma source powered with RF 13.56 MHz and operating at 6 mTorr of H2. The value of the electron-suppressor voltage (accelerating the ions) was set experimentally at U e s = − 170 V {\displaystyle U_{es}=-170V} , near the point of suppression of the secondary electron emission from the inner surface of the Faraday cup. The counting of charges collected per unit time

3154-405: The electrical conductivity . However, as a semiconductor's temperature rises above absolute zero , there is more energy in the semiconductor to spend on lattice vibration and on exciting electrons into the conduction band. The current-carrying electrons in the conduction band are known as free electrons , though they are often simply called electrons if that is clear in context. Current density

3237-458: The reference direction of the current I {\displaystyle I} . When analyzing electrical circuits , the actual direction of current through a specific circuit element is usually unknown until the analysis is completed. Consequently, the reference directions of currents are often assigned arbitrarily. When the circuit is solved, a negative value for the current implies the actual direction of current through that circuit element

3320-418: The watt (symbol: W), is equivalent to one joule per second. In an electromagnet a coil of wires behaves like a magnet when an electric current flows through it. When the current is switched off, the coil loses its magnetism immediately. Electric current produces a magnetic field . The magnetic field can be visualized as a pattern of circular field lines surrounding the wire that persists as long as there

3403-446: The AC signal. In contrast, direct current (DC) refers to a system in which the movement of electric charge in only one direction (sometimes called unidirectional flow). Direct current is produced by sources such as batteries , thermocouples , solar cells , and commutator -type electric machines of the dynamo type. Alternating current can also be converted to direct current through use of

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3486-460: The Faraday cup by oscilloscope. Proper operating conditions: h ≥ D F {\displaystyle h\geq D_{F}} (due to possible potential sag) and h ≪ λ i {\displaystyle h\ll \lambda _{i}} , where λ i {\displaystyle \lambda _{i}} is the ion free path. Signal from R F {\displaystyle R_{F}}

3569-463: The Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data was collected. One hour after the departure of the Apollo 15 Lunar Module ascent stage on August 2, 1971, the dust covers were removed and the sensors exposed directly to the lunar environment. Analysis of the two instruments' data found that the solar plasma found near to

3652-451: The Faraday cup is installed far enough away from an investigated plasma source where the flow of ions could be considered as the flow of particles with parallel velocities directed exactly along the Faraday cup axis. In this case, the elementary particle current d i i {\displaystyle di_{i}} corresponding to the ion density differential d n ( v ) {\displaystyle dn(v)} in

3735-450: The actual Faraday cup I-V characteristic i i ( U g ) {\displaystyle i_{i}(U_{g})} for processing. All of the Faraday cup elements and their assembly that interact with plasma are fabricated usually of temperature-resistant materials (often these are stainless steel and teflon or ceramic for insulators). For processing of the Faraday cup I-V characteristic , we are going to assume that

3818-424: The apparatus gains a small net charge. The cup can then be discharged to measure a small current proportional to the charge carried by the impinging ions or electrons. By measuring the electric current (the number of electrons flowing through the circuit per second) in the cup, the number of charges can be determined. For a continuous beam of ions (assumed to be singly charged) or electrons, the total number N hitting

3901-469: The assumption that we operate with a single type of ion) by the expressions where M A {\displaystyle M_{A}} is the ion mass in atomic units. The ion concentration n i {\displaystyle n_{i}} in the ion flow at the Faraday cup vicinity can be calculated by the formula which follows from Eq. ( 4 ) at U g = 0 {\displaystyle U_{g}=0} , and from

3984-549: The capacitor C F {\displaystyle C_{F}} by the saw-type voltage U g {\displaystyle U_{g}} of the sweep-generator: The current component i c ( U g ) {\displaystyle i_{c}(U_{g})} can be measured at the absence of the ion flow and can be subtracted further from the total current i Σ ( U g ) {\displaystyle i_{\Sigma }(U_{g})} measured with plasma to obtain

4067-438: The charge carriers are often electrons moving through a wire . In semiconductors they can be electrons or holes . In an electrolyte the charge carriers are ions , while in plasma , an ionized gas, they are ions and electrons. In the International System of Units (SI), electric current is expressed in units of ampere (sometimes called an "amp", symbol A), which is equivalent to one coulomb per second. The ampere

4150-412: The charge carriers, free to move about in the metal. In other materials, notably the semiconductors , the charge carriers can be positive or negative, depending on the dopant used. Positive and negative charge carriers may even be present at the same time, as happens in an electrolyte in an electrochemical cell . A flow of positive charges gives the same electric current, and has the same effect in

4233-402: The charge carriers. In a vacuum , a beam of ions or electrons may be formed. In other conductive materials, the electric current is due to the flow of both positively and negatively charged particles at the same time. In still others, the current is entirely due to positive charge flow . For example, the electric currents in electrolytes are flows of positively and negatively charged ions. In

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4316-529: The complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics . In a semiconductor it is sometimes useful to think of the current as due to the flow of positive " holes " (the mobile positive charge carriers that are places where

4399-482: The conventional condition for distribution function normalizing Fig. 2 illustrates the I-V characteristic i i ( V ) {\displaystyle i_{i}(V)} and its first derivative i i ′ ( V ) {\displaystyle i_{i}^{\prime }(V)} of the Faraday cup with S F = 0.5 c m 2 {\displaystyle S_{F}=0.5cm^{2}} installed at output of

4482-544: The correct voltages within radio antennas , radio waves are generated. In electronics , other forms of electric current include the flow of electrons through resistors or through the vacuum in a vacuum tube , the flow of ions inside a battery , and the flow of holes within metals and semiconductors . A biological example of current is the flow of ions in neurons and nerves, responsible for both thought and sensory perception. Current can be measured using an ammeter . Electric current can be directly measured with

4565-399: The cup per unit time (in seconds) is where I is the measured current (in amperes ) and e is the elementary charge (1.60 × 10 C ). Thus, a measured current of one nanoamp (10 A) corresponds to about 6 billion singly charged particles striking the Faraday cup each second. Faraday cups are not as sensitive as electron multiplier detectors, but are highly regarded for accuracy because of

4648-471: The direct relation between the measured current and number of ions. The Faraday cup uses a physical principle according to which the electrical charges delivered to the inner surface of a hollow conductor are redistributed around its outer surface due to mutual self-repelling of charges of the same sign – a phenomenon discovered by Faraday . The conventional Faraday cup is applied for measurements of ion (or electron) flows from plasma boundaries and comprises

4731-410: The energy of the ground state, the state in which electrons are tightly bound to the atomic nuclei of the material, and the free electron energy, the latter describing the energy required for an electron to escape entirely from the material. The energy bands each correspond to many discrete quantum states of the electrons, and most of the states with low energy (closer to the nucleus) are occupied, up to

4814-458: The fact that the outer shells of their atoms are bound rather loosely, and often let one of their electrons go free. Thus the interior of a metal is filled up with a large number of unattached electrons that travel aimlessly around like a crowd of displaced persons. When a metal wire is subjected to electric force applied on its opposite ends, these free electrons rush in the direction of the force, thus forming what we call an electric current." When

4897-459: The flow of conduction electrons in metal wires such as the overhead power lines that deliver electrical energy across long distances and the smaller wires within electrical and electronic equipment. Eddy currents are electric currents that occur in conductors exposed to changing magnetic fields. Similarly, electric currents occur, particularly in the surface, of conductors exposed to electromagnetic waves . When oscillating electric currents flow at

4980-410: The heavier positive ions, and hence carry the bulk of the current. The free ions recombine to create new chemical compounds (for example, breaking atmospheric oxygen into single oxygen [O 2 → 2O], which then recombine creating ozone [O 3 ]). Since a " perfect vacuum " contains no charged particles, it normally behaves as a perfect insulator. However, metal electrode surfaces can cause a region of

5063-440: The length of the wire he deduced that the heat produced was proportional to the square of the current multiplied by the electrical resistance of the wire. P ∝ I 2 R . {\displaystyle P\propto I^{2}R.} This relationship is known as Joule's Law . The SI unit of energy was subsequently named the joule and given the symbol J . The commonly known SI unit of power,

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5146-588: The load resistor R F {\displaystyle R_{F}} with a sweep generator producing saw-type pulses U g ( t ) {\displaystyle U_{g}(t)} . Electric capacity C F {\displaystyle C_{F}} is formed of the capacity of the receiver-cup – 1 to the grounded shield – 3 and the capacity of the RF cable. The signal from R F {\displaystyle R_{F}} enables an observer to acquire an I-V characteristic of

5229-623: The lunar regolith surface was broadly similar to the solar plasma measured by probes some distance from the Moon. It also found that no plasma is detectable in the shadow of the Moon during the lunar night. The instrument was also able to distinguish plasma within interplanetary space and that found in the Earth's magnetosheath . Magnetosheath plasma would exhibit large and frequent changes in plasma velocity, density and speed. Highly variable spectra were observed at lunar sunrise, potentially due to interactions with

5312-518: The lunar surface. Solar Wind Spectrometer data that was analysed after the landing of Apollo 14 , confirmed the presence of a photoelectric layer and similar in nature to that found by the Charged Particle Lunar Environment Experiment . The instrument detected a neutral gas-ion shockwave produced by the impact of the Apollo 13 S-IVB stage on the lunar surface. It was suggested that the source of this gas shockwave may be

5395-424: The metal into the vacuum. Externally heated electrodes are often used to generate an electron cloud as in the filament or indirectly heated cathode of vacuum tubes . Cold electrodes can also spontaneously produce electron clouds via thermionic emission when small incandescent regions (called cathode spots or anode spots ) are formed. These are incandescent regions of the electrode surface that are created by

5478-424: The moving electrons in metals. In certain electrolyte mixtures, brightly coloured ions are the moving electric charges. The slow progress of the colour makes the current visible. In air and other ordinary gases below the breakdown field, the dominant source of electrical conduction is via relatively few mobile ions produced by radioactive gases, ultraviolet light, or cosmic rays. Since the electrical conductivity

5561-400: The opposite direction of conventional current flow in an electrical circuit. A current in a wire or circuit element can flow in either of two directions. When defining a variable I {\displaystyle I} to represent the current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram . This is called

5644-403: The opposite direction of the electric field. The speed they drift at can be calculated from the equation: I = n A v Q , {\displaystyle I=nAvQ\,,} where Typically, electric charges in solids flow slowly. For example, in a copper wire of cross-section 0.5 mm , carrying a current of 5 A, the drift velocity of the electrons is on the order of

5727-502: The outer electrons in each atom are not bound to the individual molecules as they are in molecular solids , or in full bands as they are in insulating materials, but are free to move within the metal lattice . These conduction electrons can serve as charge carriers , carrying a current. Metals are particularly conductive because there are many of these free electrons. With no external electric field applied, these electrons move about randomly due to thermal energy but, on average, there

5810-413: The passage of an electric current through a conductor increases the internal energy of the conductor, converting thermodynamic work into heat . The phenomenon was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current through the wire for a 30 minute period. By varying the current and

5893-468: The process, it forms a light emitting conductive path, such as a spark , arc or lightning . Plasma is the state of matter where some of the electrons in a gas are stripped or "ionized" from their molecules or atoms. A plasma can be formed by high temperature , or by application of a high electric or alternating magnetic field as noted above. Due to their lower mass, the electrons in a plasma accelerate more quickly in response to an electric field than

5976-441: The range of velocities between v {\displaystyle v} and v + d v {\displaystyle v+dv} of ions flowing in through operating aperture S F {\displaystyle S_{F}} of the electron-suppressor can be written in the form where e {\displaystyle e} is elementary charge, Z i {\displaystyle Z_{i}}

6059-401: The rate at which charge flows through a given surface as: I = d Q d t . {\displaystyle I={\frac {\mathrm {d} Q}{\mathrm {d} t}}\,.} Electric currents in electrolytes are flows of electrically charged particles ( ions ). For example, if an electric field is placed across a solution of Na and Cl (and conditions are right)

6142-501: The semiconductor crystal is missing a valence electron). This is the case in a p-type semiconductor. A semiconductor has electrical conductivity intermediate in magnitude between that of a conductor and an insulator . This means a conductivity roughly in the range of 10 to 10 siemens per centimeter (S⋅cm ). In the classic crystalline semiconductors, electrons can have energies only within certain bands (i.e. ranges of levels of energy). Energetically, these bands are located between

6225-503: The semiconductor from the valence band to the conduction band depends on the band gap between the bands. The size of this energy band gap serves as an arbitrary dividing line (roughly 4 eV ) between semiconductors and insulators . With covalent bonds, an electron moves by hopping to a neighboring bond. The Pauli exclusion principle requires that the electron be lifted into the higher anti-bonding state of that bond. For delocalized states, for example in one dimension – that

6308-419: The sodium ions move towards the negative electrode (cathode), while the chloride ions move towards the positive electrode (anode). Reactions take place at both electrode surfaces, neutralizing each ion. Water-ice and certain solid electrolytes called proton conductors contain positive hydrogen ions (" protons ") that are mobile. In these materials, electric currents are composed of moving protons, as opposed to

6391-524: The sum i Σ {\displaystyle i_{\Sigma }} of the electric currents through the load resistor R F {\displaystyle R_{F}} : i i {\displaystyle i_{i}} (Faraday cup current) plus the current i c ( U g ) = − C F ( d U g / d t ) {\displaystyle i_{c}(U_{g})=-C_{F}(dU_{g}/dt)} induced through

6474-538: The surface, located around the central cup in 60-degree intervals. Each cup can measure incoming negatively charged electron flow and positively charged proton-alpha particle flow. The angle of the incoming particle was measured by using readings from all Faraday cups. Below the instrument was an electronics package located in a container with active thermal control. The electronics packages consists of power control circuits, sensor voltage control, ammeter circuits, and finally signal/data conditioning circuits. Thermal control

6557-443: The surface, thus increasing the apparent resistance. The mobile charged particles within a conductor move constantly in random directions, like the particles of a gas . (More accurately, a Fermi gas .) To create a net flow of charge, the particles must also move together with an average drift rate. Electrons are the charge carriers in most metals and they follow an erratic path, bouncing from atom to atom, but generally drifting in

6640-405: The vacuum to become conductive by injecting free electrons or ions through either field electron emission or thermionic emission . Thermionic emission occurs when the thermal energy exceeds the metal's work function , while field electron emission occurs when the electric field at the surface of the metal is high enough to cause tunneling , which results in the ejection of free electrons from

6723-418: Was collected. One hour after the departure of the Apollo 12 Lunar Module ascent stage at 15:25 on November 20, 1969, the dust covers were removed and the sensors exposed directly to the lunar environment. The Apollo 15 Solar Wind Spectrometer was deployed on the surface of the Moon on July 31, 1971, and was powered on at 19:37 UTC. It was located at 26N, 4E. The instrument's initial state had dust covers over

6806-401: Was named after Michael Faraday who first theorized ions around 1830. Examples of devices which use Faraday cups include space probes ( Voyager 1 , & 2 , Parker Solar Probe , etc.) and mass spectrometers . Faraday cups can also be used to measure charged aerosol particles. When a beam or packet of ions or electrons (e.g. from an electron beam ) hits the metallic body of the cup,

6889-405: Was provided by three radiators, a sunshield and insulation. The Apollo 12 Solar Wind Spectrometer was deployed by astronaut Pete Conrad on the surface of the Moon on November 19, 1969. It was located at 3S, 23W. The instrument's initial state had dust covers over the Faraday cup entrances. During the early phase of the experiment's activation with the dust covers in place, background baseline data

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