To determine the dielectric constant and dielectric medium by using resonant circuit of different capacitors.AimsAll the electronic devices contain different types of capacitors having different types of dielectric materials inside them. In this experiment I will determine the dielectric constant and the dielectric material used in the capacitor.

ObjectivesMy objectives for this experiment are to learn how dielectric material effects the capacitance of a capacitor and uses of different types of capacitors.

EquipmentAudio Oscillator, RLC series combination, digital meter, connecting wires, capacitors of different capacitance.

TheoryThe fundamental function of a capacitor is to store opposite polarity electrostatic charges on a pair of electrically isolated (insulated) conductive surfaces. The quantity of charge stored on each of these surfaces is ideally directly proportional to their surface areas and inversely proportional to the distance between the surfaces. Such a simple understanding needs to be refined to take into account the effect of the electric field set up between the charged plates on the insulating material. In theory this concern could be avoided by constructing capacitors without any material between: a vacuum. Unfortunately, such high vacuum devices would be impractical. The next best insulating material is air since it provides limited interacting material and a very high resistance. Air is only practical for the lowest capacitances. Other insulating materials have included: paper/oil, minerals, ceramics, glasses, ceramic corrosion layers on metals and plastic films. Any insulating material used in capacitors of identical dimensions will increase the capacitance with respect to that of a vacuum. The proportionality constant relating each material's capacitance enhancement over that of a vacuum is known as its "dielectric constant." The dielectric constant is a measure of the extent to which the insulating material's surface interacts with the electric field set up between the charged plates. The constant is dependent on two molecular level properties: the permanent "dipole moment" and the "polarizability" or the induced change in dipole moment due to the presence of an electric field. The permanent dipole moment is the average over the various dipole moments given rise to by structural charge density differences over intramolecular distances. The charge density differences result from the electronegativity differences between the various atoms which comprise the molecular structure of the insulator. Polarizability is the property which arises from changes in the 1

molecular electron distribution induced by the applied electric field. Both of these properties contribute to a net field, of opposite orientation to the inducing electric field between the charged plates. The larger the dielectric constant, the greater the induced field on the surface of the insulating material or "dielectric." In A.C. applications, where signal handling is involved, factors which affect the rates of both charging/discharging become key issues. Even though dielectrics with larger constants allow smaller size/capacitance devices, the properties of such dielectrics contribute deleteriously to audio signal processing. Where dielectrics with larger constants are employed, their larger dipole moments/polarizabilities interact more strongly with the inter-plate field, resulting in a stronger induced opposing field on the dielectric. When a capacitor is discharged across a load the polarized dipoles thermally relax in a statistical manner, exhibiting a time decay, observed as a tailing decay of residual current as complete discharge is approached. If the capacitor is suddenly discharged, allowed time to set and then shunted across a load it will discharge a residual current (of the same polarity as the initial charge). Upon dissipation of the bulk of the charge, the polarized dipoles on the dielectric thermally relax, which results in a residual charge on the plates. The residual charge from dielectric relaxation is known as the "dielectric absorption." When an audio signal is passed through a capacitor the dielectric absorption prevents full charging and discharging of the capacitor at the frequency of the alternating current signal. When the signal reverses the charging on the plates the dielectric absorption presents a lagging current of the former polarity, a hysteresis effect results. This effect becomes more acute with increasing frequency. Obviously now, not all dielectrics are equal. In audio applications it is desirable to seek the insulating material with the lowest practical dielectric absorption; hence, lowest dielectric constant, barring size and economics. Dielectric materials can be classified based on their relative polarity/polarizability properties, which the dielectric constants and dielectric absorptivities parallel. What follows is a qualitative categorization of dielectric materials in decreasing polarity/polarizability based on chemical structure considerations (Dielectric constant data "K" given when available): I. Metal oxide corrosion layers (electrolytic capacitors): 1) Tantalum oxide (K = 11) 2) Aluminum oxide (K = 7) Both consist of polar metal oxide bonds possessing large permanent dipole moments, polarizability factors are negligible. II. Ceramics and Glasses: 1) Ceramics - typically alumina or aluminosilicates (K = 4.5 - thousands) 2) Glasses - typically borosilicate (K = 4-8.5)

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Similarly, the polar inorganic oxide bonds in these materials have large permanent dipole moments. III. Minerals: 1) Mica (most common) - an alkali metal aluminosilicate, hydrate (K = 6.5 - 8.7) Same as II. IV. A. Polymer films - functionally linked - ranked in order of decreasing functional linkage polarity (brackets "[ ]" indicate guess based on functional group polarity): 1) Polyesters (ex. Mylar) - ester (K = 3.2 - 4.3) 2) [Kapton - ether and imide] 3) Polyamides (ex. Nylon) - amide (K = 3.14 -3.75) 4) Polycarbonate - carbonate (K = 2.9) 5) [PEEK - ether and ketone] 6) [Poly(phenylene oxide) - PPO - ether] 7) [Poly(phenylene sulfide) - PPS- thioether] The members of the above list can essentially be ranked based on polarity considerations alone, though polarizability considerations are significant for the latter members of the list. IV. B. Polymer films - carbon chain backbone - ranked in order of decreasing attached-group polarity/polarizability: 1) Poly(vinyl chloride) - PVC - chloro-substituted (K = 3.3 - 4.55) 2) Poly(chlorotrifluoroethylene) - chloro- and fluoro-substituted (K = 2.48 - 2.76) 3) Poly(p-phenyleneethylene) - Parylene - exception to list phenyl ring in backbone (K = 2.65) 4) Polystyrene - phenyl-substituted (K = 2.54 - 2.56) 5) Polyethylene - essentially unsubstituted carbon chain (K = 2.3 - 2.37) 6) Polypropylene - methyl-substituted (K = 2.1) 7) Poly(tetrafluoroethylene) (ex. Teflon) - perfluoro-substituted (K = 2.0 - 2.1) To rank the first two members of this list consideration must be given to both, polarity and polarizability considerations. Polymer 2) is adequately fluorinated to cancel C-F bond polarities, the C-Cl bonds are the prime contributors to its polarity. Since C-F bonds are not verypolarizable, polymer 1) has a higher polarizability than polymer 2) and a correspondingly higher dielectric constant. Polymers 3) and 4) can be ranked primarily on their polarizabilities, which are significantly higher due to the pi-electrons in their phenyl moieties. Polymers 5 and 6 differ mainly in that the methyl substituted chains are less prone to wrap against themselves due to steric methyl-methyl interactions. In Teflon the C-F bond polarities essentially cancel since it is completely fluorinated, and given

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that the C-F bonds are not very polarizable it exhibits overallless polarizability than its unsubstituted carbon chain analogue, 5), polyethylene. Based on polarization/dielectric constant considerations for minimization of dielectric absorption, the best films for audio applications are teflon and polypropylene. Runners up would be polyethylene and polystyrene, based on these considerations alone. Throughout this discussion, I have assumed that dielectric absorption and the dielectric constant are directly correlated. Apparently, when polarizability factors predominate, the time constant for relaxation of the field induced dipole is critical. Otherwise, one would expect polypropylene to have a lower dielectric absorption than polystyrene, which is not the observed result. This can be reasoned by re-examining what is being polarized by the field in each. In the case of the polystyrene, the pi-electrons in the aromatic rings (which have been modeled, in the past, as a "free electron gas") can orient electronically, with less mechanical change in the polymer structure. Hence, it can relax faster. In contrast, the polarization of polypropylene involves more mechanical change of the structure, and hence a slower relaxation rate. Up to this point, I have only mentioned in passing paper/oil (paper-in-oil) capacitors. These classic devices from "days of yore" are making a comeback in some audio circles especially among tube connoisseurs. Certainly, they are of interest. Unfortunately, they employ a composite dielectric that consists of a paper spacer/absorbent saturated with an oil; therefore, they do not readily lend themselves to the present simple analysis. Since the dielectric polarization primarily occurs on the surface of the dielectric material, in the vicinity of the plates, the dielectric constant in such a capacitor would consist of a weighted average of two dielectric constants: the most significant weighting attributed to the oil and the lesser weighting attributed to the surface area of the fibrules of paper in contact with the metal plates. The weightings for each dielectric component are not readily measurable. Hence, all that we know is that the contribution of the paper cannot be neglected, since it acts as a supporting spacer for the tightly rolled foil plates and makes intimate contact with them. One should measure the dielectric constant for each type of paper/oil combination under consideration. The most common combination is that of a petroleum derived mineral oil absorbed into kraft paper. Common foils include aluminum and tin. More "exotic" variants on this theme, are those capacitors distributed by a certain manufacturer/distributor in England (whos name shall remain omitted here), which consist of a vegetable oil/unspecified type paper dielectric and copper or silver foil plates. [It should be noted that the same British manufacturer also sells a series of mylar film (K = 4)/foil capacitors for signal handling: a pecular dielectric material for high cost/performance audio signal carrying applications.] The nature of the plate metal is not nearly as important as that of the oil and the paper. Mineral oils, consist mainly of saturated hydrocarbon oils and exhibit very low dielectric constants near K = 2. In contrast, papers such as Kraft paper exhibit dielectric constants on the order of K = 4. If we assume a mere 10% paper-plate contact, the composite dielectric constant would be near K = 2.2; which is similar to that of polypropylene. The

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10% figure is merely an arbitrary suggestion. Unfortunately, one would expect two superimposed polarization thermal relaxation rates: that associated with the polar solid cellulosic paper would be significantly slower than that for the non-polar liquid mineral oil. In contrast, the relaxation rate for a non-polar polymer film such as polypropylene would be nearer that of mineral oil than that of paper; and its relaxation characteristics would be more uniform due to its homogeneous nature. The use of vegetable oil in place of the mineral oil only makes matters worse for the paper/oil composite dielectric; since vegetable oil, as a fatty acid ester, would exhibit a dielectric constant in the vicinity of K = 3. If we again assume 10% paper-foil contact, the composite dielectric constant would be near K = 3.1. (Perhaps such capacitors might be better suited for the culinary arts!)

MethodologyTo perform this experiment I connected the RLC series combination with audio oscillator with the help of wires after completely checking that the circuit is set properly I started to take readings with regular steps. After taking readings with one capacitor I repeated this experiment with different capacitors. After finishing this I plotted the graphs and calculated the dielectric constant and find the dielectric material.

Observations for the capacitor having capacitance 104 pFobs. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Ferquency Hz 36 55 80 110 145 180 210 250 300 480 750 900 1125 1325 1700 2400 3800 6500 12000 log f Current mA 1.55 2.5 1.74 5 1.9 7.5 2.04 10 2.16 12.5 2.26 15 2.34 17.5 2.4 20 2.48 22.5 2.68 24 2.88 22.5 2.95 20 3.05 17.5 3.12 15 3.23 12.5 3.38 10 3.58 7.5 3.81 5 4.1 2.5

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Observations for the capacitor having capacitance 103 pF

obs. No. Ferquency Hz obs. No. 1 Ferquency7000 Hz 1 360 2 9250 2 475 3 10000 3 625 4 11600 4 900 5 14000 5 1150 6 15000 6 1450 7 21000 7 1750 8 29000 8 2450 9 31000 9 5000 10 32000 10 9500 11 42500 11 16500

log f Current mA log 3.85 Current mA f 2.5 2.56 5 3.97 4 2.68 7.5 4 5 2.8 10 4.06 6 2.95 15 4.15 7.5 3.1 20 4.18 8 3.16 22.5 4.32 10 3.24 20 4.46 8 3.4 15 4.49 7.5 3.7 10 4.51 6 3.98 7.5 4.63 5 4.22 5

Observations for the capacitor having capacitance 101 pF

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obs. No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Ferquency Hz 240 380 500 690 850 1000 1075 1275 1600 2000 2400 2900 3800 6000 10250 17000 26000

log f Current mA 2.38 2.5 2.58 5 2.7 7.5 2.84 10 2.93 12.5 3 15 3.03 17.5 3.11 20 3.2 22.5 3.3 20 3.38 17.5 3.46 15 3.6 12.5 3.78 10 4.01 7.5 4.23 5 4.41 2.5

Observations for the capacitor having capacitance unknown pF

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CalculationsFrom the graphs the resonance frequencies of the different capacitors are

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500 Hz of 104 pF 1413 Hz of 103 pF 20892 Hz of 101 pF and 1585 Hz of unknown capacitance. Now we can calculate the dielectric constant by dividing all the frequencies by minimum frequency So 500 = 1 . error 0% 500 Medium is air or Vacuum. 0 = 1413 = 2.8 , error 4.8% 500 the dielectric material is rubber. 1 = 20892 = 41.78 , error 1.7 % 500 medium is glycerine. 2 = 1585 = 3.17 , error 0.3 % 500 medium is vinylite. 3 =

SuggestionsDuring these experiments I faced some difficulties on the basis of those difficulties I have some suggestions which I like to give so that other people can do these experiments easily.

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Before performing an experiment stud it completely so that u can understand it aims and objective and u can perform it easily. To avoid errors in the readings take the reading carefully and before starting the experiment make sure that u have set the apparatus correctly. During the experiment dont ignore the safety rules to avoid from any mishap.

QuestionsQuestion 1: what is impedance ? 10

Ans. The total impedance Z presented by the passive elements ( resistors, capacitors and inductors )of a circuit is defined as the ratio Z=V/I and is also a phasor with a real and imaginary components. Question 2 : why is a RLC series circuit is called an acceptor circuit ? Ans. A given combination of R ,L and C in series allows the current to flow in a certain frequency range only, it also accepts some specific frequencies thats why it is called acceptor circuit. Question 3: what is quality Factor ? Ans. It is the ratio between resonance frequency and the band width. Question 4: What is the practical use of RLC series circuit ? Ans. An acceptor circuit is used for tuning radio and television. Question 5: What are the characteristics of a acceptor circuit. Ans. A good acceptor is one which has a very small band width and large quality factor. Question 6: What is meant by admittance ? Ans. Admittance is the reciprocal of the circuit. Question 7 : why RLC parallel circuit is also called a rejecter circuit. Ans. It rejects signal of only one frequency or has minimum response but gives high response at other frequencies. Question 8: what Is meant by resonant frequency of a RLC series circuit. Ans. The resonance frequency of a RLC series circuit is one for which the impedance of the circuit is minimum and maximum current flows through it. Question 9 : What is meant by the suitable range of the meter. Ans. The most suitable range for measuring a certain quantity is the one for which full scale deflection is nearly equal to the value being measured. Question 10 : what is meant by resonance in RLC parallel circuit ? Ans. For a certain frequency of the sinusoidal voltage applied to the RLC parallel circuit, the current flowing in the circuit has a minimum value this phenomenon is known as resonance.

To verify the Longmeir relation using ionization potential of mercury.11

AimsAim of this experiment is to verify the longmeir relation .

ObjectivesThe objective of this experiment is to check how electronic devices depend on temperature.

EquipmentMercury diode, voltmeter, variable micro-ammeter, power supply.

Theory Element Mercury, Hg, Transition MetalMercury History 80 [Xe] Mercury was known by Chinese and in Hindus even Hg 6s2 2000 years BC. Cinnabar (HgS), the mercury ore, was easily 200.59 4f14 isolated and widely used in these countries as well as by Mercury 5d10 Greeks and Romans as a pigment (vermilion), remedy and in cosmetics. Dioscorides, the Greek physician of 1st century AD, extracted it from cinnabar distilling it on the iron lid of the vessel. It was called hydrargyros from hydor meaning water, and argyros that is silver, which was borrowed in Latin as hydrargyrum. The original Latin name was argentum vivum - living silver (quicksilver in English). Mercury Occurrence Mercury is a trace element with abundance 7.0x10-6 mass % in Earth's crust, 1.03 mg/m3 in sea water and 2x10-3mg/m3 in atmosphere. It occurs as a native metal and forms more than 30 minerals with cinnabar (HgS) as the most common ore.Mercury minerals as isomorphous additions may be found in quartz, chalcedony, carbonates, micas and lead-zinc ores. Bulks of mercury participate in exchange processes which take place in atmosphere, hydrosphere and lithosphere. It is dispersed in biosphere being accumulated in insignificant quantities in clay and silt, reaching 4x10-5% in clays and micas. Sea water contains 3x10-9% of mercury. Mercury deposits are evaluated as 500 thousand tons as a whole, including 250 in Spain, 100 in Italy, 50 in USA, 15 in Canada, 15 in Mexico, 9 in Turkey, and 8 in Algeria. Significant deposits are located in Japan, Bolivia, Peru, China, and Slovakia. Ores contain from 0.05 to 6-7% ofmercury.

Mercury IsotopesProton number: 80

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Mercury Stable Isotopes Mercury stable isotope number 1: 196Hg Neutrons: 116; Abundance: 0.15%; Jn: 0+; Mercury stable isotope number 2: 198Hg Neutrons: 118; Abundance: 9.97%; Jn: 0+; Mercury stable isotope number 3: 199Hg Neutrons: 119; Abundance: 16.87%; Jn: 1/2-; Mercury stable isotope number 4: 200Hg Neutrons: 120; Abundance: 23.1%; Jn: 0+; Mercury stable isotope number 5: 201Hg Neutrons: 121; Abundance: 13.18%; Jn: 3/2-; Mercury stable isotope number 6: 202Hg Neutrons: 122; Abundance: 29.86%; Jn: 0+;

Mercury stable isotope number 7: 204Hg Neutrons: 124; Abundance: 6.87%; Jn: 0+;

Mercury Natural Radioactive isotopes13

There is no Mercury Natural Radioactive isotopes known.

Mercury Artificial Radioactive isotopesMercury radioactive isotope number 1: 171Hg Neutrons: 91; Jn: Unknown; Decay: ~ 100.00 %; t1/2: 5.9E-05s 59.00 s; Mercury radioactive isotope number 2: 172Hg Neutrons: 92; Jn: 0+; Decay: ; t1/2: 0.00025s 0.25 ms; Mercury radioactive isotope number 3: 173Hg Neutrons: 93; Jn: Unknown; Decay: ~ 100.00 %; t1/2: 0.0006s 0.60 ms; Mercury radioactive isotope number 4: 174Hg Neutrons: 94; Jn: 0+; Decay: : 99.60 %; t1/2: 0.0021s 2.10 ms;

Mercury radioactive isotope number 5: 175Hg Neutrons: 95; Jn: 7/2-,9/2-; Decay: : 100.00 %; t1/2: 0.0108s 10.80 ms; Mercury radioactive isotope number 6: 176Hg Neutrons: 96; Jn: 0+;

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Decay: t1/2:

: 94.00 %; 0.0203s 20.30 ms;

Mercury radioactive isotope number 7: 177Hg Neutrons: 97; Jn: 13/2+; Decay: : 85.00 % : 15.00 %; t1/2: 0.1273s ; Mercury radioactive isotope number 8: 178Hg Neutrons: 98; Jn: 0+; Decay: ~ 70.00 % ~ 30.00 %; t1/2: 0.269s ; Mercury radioactive isotope number 9: 179Hg Neutrons: 99; Jn: Unknown; Decay: ~ 53.00 % ~ 47.00 % p ~ 0.15 %; t1/2: 1.08s ; Mercury radioactive isotope number 10: 180Hg Neutrons: 100; Jn: 0+; Decay: : 52.00 % : 48.00 %; t1/2: 2.58s ; Mercury radioactive isotope number 11: 181Hg Neutrons: 101; Jn: 1/2-; Decay: : 73.00 % : 27.00 % p : 0.01 % : 9.0E-6 %; t1/2: 3.6s ; Mercury radioactive isotope number 12: 182Hg Neutrons: 102;

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Jn: Decay: t1/2:

0+; : 84.80 % : 15.20 %; 10.83s ;

Mercury radioactive isotope number 13: 183Hg Neutrons: 103; Jn: 1/2-; Decay: : 88.30 % : 11.70 % p : 2.6E-4 %; t1/2: 9.4s ; Mercury radioactive isotope number 14: 184Hg Neutrons: 104; Jn: 0+; Decay: : 98.89 % : 1.11 %; t1/2: 30.9s ; Mercury radioactive isotope number 15: 185Hg Neutrons: 105; Jn: 1/2-; Decay: : 94.00 % : 6.00 %; t1/2: 49.1s ;

Mercury radioactive isotope number 16: 185Hg Neutrons: 105; Jn: 13/2+; Decay: IT : 54.00 % : 46.00 % ~ 0.03 %; t1/2: 21.6s ; Mercury radioactive isotope number 17: 186Hg Neutrons: 106; Jn: 0+; Decay: : 99.98 % : 0.02 %; t1/2: 82.8s ;

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Mercury radioactive isotope number 18: 187Hg Neutrons: 107; Jn: 13/2+; Decay: : 100.00 % > 1.2E-4 %; t1/2: 144s 2.40 m; Mercury radioactive isotope number 19: 187Hg Neutrons: 107; Jn: 3/2-; Decay: : 100.00 % > 2.5E-4 %; t1/2: 114s ; Mercury radioactive isotope number 20: 188Hg Neutrons: 108; Jn: 0+; Decay: : 100.00 % : 3.7E-5 %; t1/2: 195s 3.25 m;

Mercury radioactive isotope number 21: 189Hg Neutrons: 109; Jn: 3/2-; Decay: : 100.00 % < 3.0E-5 %; t1/2: 456s 7.60 m; Mercury radioactive isotope number 22: 189Hg Neutrons: 109; Jn: 13/2+; Decay: : 100.00 % < 3.0E-5 %; t1/2: 516s 8.60 m; Mercury radioactive isotope number 23: 190Hg Neutrons: 110; Jn: 0+; 17

Decay: t1/2:

: 100.00 % < 3.4E-7 %; 1200s 20.00 m;

Mercury radioactive isotope number 24: 191Hg Neutrons: 111; Jn: 3/2-; Decay: : 100.00 %; t1/2: 2940s 49.00 m; Mercury radioactive isotope number 25: 191Hg Neutrons: 111; Jn: 13/2+; Decay: : 100.00 %; t1/2: 3048s 50.80 m; Mercury radioactive isotope number 26: 192Hg Neutrons: 112; Jn: 0+; Decay: : 100.00 %; t1/2: 17460s 4.85 h; Mercury radioactive isotope number 27: 193Hg Neutrons: 113; Jn: 3/2-; Decay: : 100.00 %; t1/2: 13680s 3.80 h; Mercury radioactive isotope number 28: 193Hg Neutrons: 113; Jn: 13/2+; Decay: : 92.80 % IT : 7.20 %; t1/2: 42480s 11.80 h; Mercury radioactive isotope number 29: 194Hg Neutrons: 114; Jn: 0+; Decay: : 100.00 %; t1/2: 14001980000s 444.00 y; Mercury radioactive isotope number 30: 195Hg

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Neutrons: Jn: Decay: t1/2:

115; 1/2-; : 100.00 %; 37908s 10.53 h;

Mercury radioactive isotope number 31: 195Hg Neutrons: 115; Jn: 13/2+; Decay: IT : 54.20 % : 45.80 %; t1/2: 149760s 41.60 h; Mercury radioactive isotope number 32: 197Hg Neutrons: 117; Jn: 1/2-; Decay: : 100.00 %; t1/2: 230904s 2.67 d;

Mercury radioactive isotope number 33: 197Hg Neutrons: 117; Jn: 13/2+; Decay: IT : 91.40 % : 8.60 %; t1/2: 85680s 23.80 h; Mercury radioactive isotope number 34: 199Hg Neutrons: 119; Jn: 13/2+; Decay: IT : 100.00 %; t1/2: 2560.2s 42.67 m; Mercury radioactive isotope number 35: 203Hg Neutrons: 123; Jn: 5/2-; Decay: - : 100.00 %; t1/2: 4025722s 46.59 d; Mercury radioactive isotope number 36: 205Hg Neutrons: 125; Jn: 1/2-; Decay: - : 100.00 %;

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t1/2:

308.4s 5.14 m;

Mercury radioactive isotope number 37: 206Hg Neutrons: 126; Jn: 0+; Decay: - : 100.00 %; t1/2: 489s 8.15 m; Mercury radioactive isotope number 38: 207Hg Neutrons: 127; Jn: 9/2+; Decay: - : 100.00 %; t1/2: 174s 2.90 m;

Mercury radioactive isotope number 39: 208Hg Neutrons: 128; Jn: 0+; Decay: - : 100.00 %; t1/2: 2460s 41.00 m; Mercury radioactive isotope number 40: 209Hg Neutrons: 129; Jn: Unknown; Decay: - : 100.00 %; t1/2: 37s ; Mercury radioactive isotope number 41: 210Hg Neutrons: 130; Jn: 0+; Decay: - ?; t1/2: 3E-07s 0.30 s;

Atomic Data for Mercury (Hg)Atomic Number = 80, Atomic Weight = 200.59, Reference E95

Isotope

Mass

Abundance

Spin

Mag Moment

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Isotope 196 Hg 198 Hg 199 Hg 200 Hg 201 Hg 202 Hg 204 Hg

Mass 195.965807 197.966743 198.968254 199.968300 200.970277 201.970617 203.973467

Abundance 0.15% 10.1% 17.0% 23.1% 13.2% 29.65% 6.85%

Spin 0 0 1/2 0 3/2 0 0

Mag Moment +0.5059 -0.5602

Hg I Ground State 1s22s22p63s23p63d104s24p64d104f145s25p65d106s2 1S0 Ionization energy 84184.1 cm-1 (10.4375 eV) Ref. B83 Hg II Ground State 1s22s22p63s23p63d104s24p64d104f145s25p65d106s 2S1/2 Ionization energy 151284.4 cm-1 (18.7568 eV) Ref. SR01

Mercury ProductionMercury ore processing includes oxidizing roasting of cinnabar: HgS + O2 = Hg + SO2. Roast gas pass through dust chamber and enter the tubular cooler made of stainless steel or Monel metal. Liquid mercurydrips into iron receivers. It is refined as the liquid mercurythread flows through the 1-1.5 m tall tower with 10% HNO3, flush with water, dried up and sublimated in vacuum. Hydrometallurgical extraction of mercury from ores and concentrates is also possible. The process includes HgSdissolving in sodium sulphite following with mercury substitution by aluminium. Methods of mercury production by sulphide solutions electrolysis are also worked out.

Mercury ApplicationsMercury is an excellent media for temperature measurement due to its enormous temperature range: it freezes at -38.9C and boils at 356.7C; moreover, the boiling point grows on a hundred degrees as the pressure increases. Then, the wettability of mercury on glass is very low, which increases the measurement accuracy. The most important of mercury properties is that its thermal expansion proceeds much more uniformly than that of other liquids. And, finally, mercury has a very small specific heat: it may be warmed 30 times faster than the water. In other words mercury thermometer has a very fast response. Despite the toxicity it is still impossible to stop utilization of mercury and its compounds. Mercury applications are very vast. Metal mercury is used in electric contacts, diffusion vacuum pump switches, in rectifiers, barometers, thermometers, in mercury cathodes used in caustic soda and chlorine production, in dry batteries which contain mercury oxide or zinc or cadmium amalgam. 21

Mercury is used also in mercury-vapor lamps.

Ionization potentialThe ionization potential, ionization energy or EI of an atom or molecule is the energy required to remove an electron from the isolated atom or ion. More generally, the nth ionization energy is the energy required to strip it of the nth electron after the first n 1 electrons have been removed. It is considered a measure of the "reluctance" of an atom or ion to surrender an electron, or the "strength" by which the electron is bound; the greater the ionization energy, the more difficult it is to remove an electron. The ionization potential is an indicator of the reactivity of an element. Elements with a low ionization energy tend to be reducing agents and to form salts.

Ionization potential of MercuryIonization potential of mercury is 1. Ionization potential: 10.4375 eV 2. Ionization potential: 18.759 eV 3. Ionization potential: 34.202 eV

Longmeir RelationThe longmeir relation for the current and voltage is given below I p = KV p K= Ip3 3 2

Vp 2 where I p is the anode current and V p is the applied anode voltage and K is constant equal to 1.5 .

RecipeTo verify the longmeir relation using ionization potential of mercury I just took the apparatus of ionization potential of mercury and powered on. Now I started increasing the voltage and noted the values of current flowing I draw the graph and calculated the values of K from the Graph and then compared it with the actual value of K .

Observations

Obs. No.

Vp

log V p 2

3

Ip

log I p

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1 2 3 4 5 6

1 2 3 4 5 6

0 0.45 0.72 0.9 1.05 1.17

5 10 17 22 30 110

.7 1 1.23 1.34 1.48 2.04

CalculationsDifferent values of K from graph are 0.91 = 2.84 0.32 1.06 K2 = = 1.96 0.54 1.27 K3 = = 1.58 0.8 1.42 K4 = = 1.42 1 1.75 K5 = = 1.56 1.12 K + K 2 + K 3 + K 4 + K5 mean value of K = 1 5 = 1.872 K1 = actual value of K = 1.5 Difference Percent error = 0.37 = 24.67 %

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Sources of Errors and PrecautionsThe error may be occur due to wrong measurement because the voltmeter is not digital so there may be a little error while taking a reading .So be careful while taking reading. For the filament rating of the tube , tube manual should be consulted. Filament voltage should not exceed the rated value and it should remain constant. High impedance voltmeter should be used for measuring plate voltage. Near ionization point , the plate voltage should be increased very slowly and care should be taken to limit the plate current to maximum value that can be measured with the voltmeter used. Mercury is highly toxic in both liquid and gaseous forms. This is a toxic heavy metal that causes brain and liver damage if it is ingested. For this reason, thermometers which are only intended to measure typical climatic temperatures now use pigmented alcohol instead; the boiling point of alcohol is higher than any natural temperature expected on Earth. Some medical thermometers still use mercury, for reason of accuracy. Care must be exercised not to bite such a thermometer. The commercial unit for handling mercury is the "flask," which weighs 76 lb. Mercury is a very dangerous bioaccumulative toxin that is easily absorbed through skin, respiratory and gastrointestinal tissues. Minamata disease is a form of mercury poisoning. Mercury attacks the central nervous system and adversely affects the mouth, gums, and teeth. High exposure over long periods of time will result in brain damage and ultimately death. Air saturated with mercury vapor at room temperature is at a concentration many times the toxic level, despite the high boiling point (the danger is increased at higher temperatures). Mercury should therefore be handled with great care. Containers of mercury need to be covered securely to avoid spillage and evaporation. Heating of mercury or mercury compounds should always be done under a wellventilated hood; some oxides in particular can decompose into elemental mercury, which immediately evaporates and may not be obvious. 24

DiscussionFrom this experiment we can conclude that all the electronic devices are temperature dependent and with the variation in temperature conductivity of the materials varies.

QuestionsWhy's Mercury In Fluorescent Bulbs?Mercury is an essential ingredient for most energy-efficient lamps. Fluorescent lamps and high intensity discharge (HID) lamps are the two most common types of lamps that utilize mercury. Fluorescent lamps provide lighting for most schools, office buildings and stores. HID lamps, which include mercury-vapor, metal halide and high-pressure sodium lamps, are used for street lights, floodlights and industrial lighting. A typical fluorescent lamp is composed of a phosphor-coated glass tube with electrodes located at either end. The tube contains mercury, of which only a very small amount is in vapor form. When a voltage is applied, the electrodes energize the mercury vapor, causing it to emit ultraviolet (UV) energy. The phosphor coating absorbs the UV energy, causing the phosphor to fluoresce and emit visible light. Without the mercury vapor to produce UV energy, there would be no light. A four-foot fluorescent lamp has an average rated life of at least 20,000 hours. To achieve this long life, lamps must contain a specific quantity of mercury. The amount of mercury required is very small, typically measured in milligrams, and varies by lamp type, date of manufacture, manufacturing plant and manufacturer.

What is excitation potential?It is that accelerating potential which imparts to the impinging electron enough energy to make an electron of the impacted atom to move from the normal to higher orbit.

What is ionization potential ?It is that accelerating potential which makes an impinging electron acquire sufficient energy to knock electron to right out of the atom thereby ionizing the atom.

Define electron volt ?It is the unit of energy used in atomic physics. It is the energy acquired by an electron in falling freely through a potential difference of one volt.

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Can there be more than one ionization potentials for the same kind of atom ?Yes, they are called 1st ionization potential, 2nd ionization potential etc. according as the atom is singly ionized, doubly ionized etc. As an example Helium has two ionization potentials of 24.5 and 78.6 volts.

Why does the plate current show a sudden rise ?Because at ionizing value of potential, positive ions are formed, which on account of their low mobility, are very effective in neutralizing the electron space charge, thereby resulting in an increased plate current.

What is Ionization?Ionization is the physical process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This process works slightly differently depending on whether an ion with a positive or a negative electric charge is being produced. A positively charged ion is produced when an electron bonded to an atom (or molecule) absorbs enough energy to escape from the electric potential barrier that originally confined it, thus breaking the bond and freeing it to move. The amount of energy required is called the ionization potential. A negatively charged ion is produced when a free electron collides with an atom and is subsequently caught inside the electric potential barrier, releasing any excess energy. Ionization can generally be broken down into two types: sequential ionization and nonsequential ionization.

So what is an ion?An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion ( ana: Greek 'up') (pronounced /nan/; an-eye-on). Conversely, a positively-charged ion, which has fewer electrons than protons, is known as a cation ( kata: Greek 'down') (pronounced /ktan/; cat-eye-on). An ion consisting of a single atom is called a monatomic ion, but if it consists of two or more atoms, it is a polyatomic ion. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions. Ions are denoted in the same way as electrically neutral atoms and molecules except for the presence of a superscript indicating the sign of the net electric charge and the number of electrons lost or gained, if more than one. For example: H+ and SO42.

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An electrostatic potential map of the nitrate ion (NO3). Areas coloured red are lower in energy than areas colored yellow

To Study the Characteristics of Geiger-Muller counter.AimGeiger-Muller is radiation counter device. And using a radiatin source I will count the radiations per minute. Also I will study the characteristics of Geiger-Muller counter and try to know how it works

ObjectiveBecome familiar with the sources of radiation around us, and measure the level of radiation emitted from them.

EquipmentGeiger-Muller counter Electronic counting device or Scalar A.C main Source of Radiation Stop Watch

Theory Geiger-Muller CounterA Geiger counter, also called a Geiger-Mller counter, is a type of particle detector that measures ionizing radiation.

Description

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Geiger counters are used to detect radiation usually gamma and beta radiation, but certain models can also detect alpha radiation. The sensor is a Geiger-Mller tube, an inert gas-filled tube (usually helium, neon or argon with halogens added) that briefly conducts electricity when a particle or photon of radiation temporarily makes the gas conductive. The tube amplifies this conduction by a cascade effect and outputs a current pulse, which is then often displayed by a needle or lamp and/or audible clicks. Modern instruments can report radioactivity over several orders of magnitude. Some Geiger counters can also be used to detect gamma radiation, though sensitivity can be lower for high energy gamma radiation than with certain other types of detector, because the density of the gas in the device is usually low, allowing most high energy gamma photons to pass through undetected (lower energy photons are easier to detect, and are better absorbed by the detector. Examples of this are the X-ray Pancake Geiger Tube). A better device for detecting gamma rays is a sodium iodide scintillation counter. Good alpha and beta scintillation counters also exist, but Geiger detectors are still favored as general purpose alpha/beta/gamma portable contamination and dose rate instruments, due to their low cost and robustness. A variation of the Geiger tube is used to measure neutrons, where the gas used is Boron Trifluoride and a plastic moderator is used to slow the neutrons. This creates alpha particle inside the detector and thus neutrons can be counted.

A modern geiger counter Other names Geiger-Mller counter Uses Particle detector Inventor Hans Geiger Related items Geiger-Mller tube

HistoryCold War-era survey meter (this is an ion chamber, not a Geiger counter) Hans Geiger developed a device (that would later be called the "Geiger counter") in 1908 together with Ernest Rutherford. This counter was only capable of detecting alpha particles. In 1928, Geiger and Walther Mller (a PhD student of Geiger) improved the counter so that it could detect all kinds of ionizing radiation. The current version of the "Geiger counter" is called the halogen counter. It was invented in 1947 by Sidney H. Liebson (Phys. Rev. 72, 602608 (1947)). It has superseded the 28

earlier Geiger counter because of its much longer life. The devices also used a lower operating voltage. http://www.national-radiation-instrument-catalog.com History of Portable Radiation Detection Instrumentation from the period 1920-1960

Geiger-Mller tubeA Geiger-Mller tube (or GM tube) is the sensing element of a Geiger counter instrument that can detect a single particle of ionizing radiation, and typically produce an audible click for each. It was named for Hans Geiger who invented the device in 1908, and Walther Mller who collaborated with Geiger in developing it further in 1928.[1] It is a type of gaseous ionization detector with an operating voltage in the Geiger plateau. The Geiger counter is sometimes used as a hardware random number generator

Description and operationA Geiger-Mller tube consists of a tube filled with an low-pressure (~0.1 Atm) inert gas such as helium, neon or argon, in some cases in a Penning mixture, and an organic vapor or a halogen gas and contains electrodes, between which there is a voltage of several hundred volts, but no current flowing. The walls of the tube are either metal or the inside coated with metal or graphite to form the cathode while the anode is a wire passing up the center of the tube. When ionizing radiation passes through the tube, some of the gas molecules are ionized, creating positively charged ions, and electrons. The strong electric field created by the tube's electrodes accelerates the ions towards the cathode and the electrons towards the anode. The ion pairs gain sufficient energy to ionize further gas molecules through collisions on the way, creating an avalanche of charged particles. This results in a short, intense pulse of current which passes (or cascades) from the negative electrode to the positive electrode and is measured or counted. Most detectors include an audio amplifier that produce an audible click on discharge. The number of pulses per second measures the intensity of the radiation field. Some Geiger counters display an exposure rate (e.g. mRh), but this does not relate easily to a dose rate as the instrument does not discriminate between radiation at different energy.

Working Principle of Geiger-Muller counterThe Geiger-Mller tube works on the same principle as the spark counter: an ionization between two high voltage electrodes produces a pulse of current (an avalanche of charge) between the electrodes. The differences are that the Geiger-Mller tube is sealed, it contains a low pressure gas (usually argon with a little bromine), and it is usually part of a circuit with a scalar counter. The scalar counter records and counts each pulse of charge.

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The actual phenomena inside a tube are much more complicated than the simple story of ionization producing an avalanche of electrons. Inside the tube ultra violet photons probably play an important part, as well as colliding electrons and ions, and the detailed picture is extremely complex. An ionizing particle will produce a pulse of charge of almost constant size. The size of the pulse does not vary with the energy or amount of ionization produced by the ionizing particle. The number of pulses represents the number of ionizing particles coming into the tube. Geiger-Mller tubes do not distinguish between one kind of particle and another, or between a more energetic particle and a less energetic one, provided the particle enters the tube and does not pass right through.

GM tubesThe usual form of tube is an end-window tube. This type is so-named because the tube has a window at one end through which ionizing radiation can easily penetrate. The other end normally has the electrical connectors. There are two types of end-window tubes: the glass-mantle type and the mica window type. The glass window type will not detect alpha radiation since it is unable to penetrate the glass, but is usually cheaper and will usually detect beta radiation and X-rays. The mica window type will detect alpha radiation but is more fragile. Most tubes will detect gamma radiation, and usually beta radiation above about 2.5 MeV. Geiger-Mller tubes will not normally detect neutrons since these do not ionise the gas. However, neutron-sensitive tubes can be produced which either have the inside of the tube coated with boron or contain boron trifluoride or helium-3 gas. The neutrons interact with the boron nuclei, producing alpha particles or with the helium-3 nuclei producing hydrogen and tritium ions and electrons. These charged particles then trigger the normal avalanche process.

QuenchingThe G.M. tube must produce a single pulse on entry of a single particle.It must not give any spurious pulse and recover quickly to the passive state.But unfortunately the positive Ar ions that eventually strike the cathode become neutral Ar atoms in an excited state by gaining electrons from the cathode. The excited atoms return to the ground state by emitting photons and these photons cause avalanches and hence spurious pulses. To prevent the current from flowing continuously there are several techniques to stop, or quench the discharge. Quenching is important because a single particle entering the tube is counted by a single discharge, and so it will be unable to detect another particle until the discharge has been stopped, and because the tube is damaged by prolonged discharges. External quenching uses external electronics to remove the high voltage between the electrodes. Self-quenching or internal-quenching tubes stop the discharge without

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external assistance, and contain a small amount of a polyatomic organic vapor such as butane or ethanol; or alternatively a halogen such as bromine or chlorine. If the diatomic gas(quencher) is introduced in the tube, the positive Ar ions, during their slow motion to the cathode, would have multiple collisions with the quencher gas molecules and transfer their charge and some energy to them. Thus neutral Ar atoms would reach the cathode. The quencher gas ions in their turn reach the cathode, gain electrons thereform and move into excited states. But these excited molecules lose their energy not by photon emission but by dissociation into neutral quencher molecules.[2] No spurious pulses are thus produced.

Invention of halogen tubesThe halogen tubes were invented by Sidney H. Liebson in 1947, and are now the most common form, since the discharge mechanism takes advantage of the metastable state of the inert gas atom to ionize the halogen molecule and produces a more efficient discharge which permits it to operate at much lower voltages, typically 400600 volts instead of 9001200 volts. It also has a longer life because the halogen ions can recombine whilst the organic vapor cannot and is gradually destroyed by the discharge process (giving the latter a life of around 108 events).

Types and applicationsThe configuration of GM tubes determines the types of radiation that it can detect. For example, a thin mica window on a GM Tube (shown here) will allow for the detection of alpha radiation, where as GM Tubes without a thin mica window are too thick for the alpha and low energy beta radiation to pass through and be detected. The Geiger-Mller tube is one form of a class of radiation detectors called gaseous detectors or simply gas detectors. Although useful, cheap and robust, a counter using a GM tube can only detect the presence and intensity of radiation (particle frequency, as opposed to energy). Gas detectors with the ability to both detect radiation and determine particle energy levels (due to their construction, test gas, and associated electronics) are called proportional counters. Some proportional counters can detect the position and or angle of the incident radiation as well. Other devices detecting radiation include: ionization chamber, dosimeters, photomultiplier, semiconductor detectors and variants including CCDs, microchannel plates, scintillation counters, solid-state track detectors, cloud chambers, bubble chambers, spark chambers, neutron detectors and microcalorimeters. The Geiger-Mller counter has applications in the fields of nuclear physics, geophysics (mining) and medical therapy with isotopes and x-rays. Some of the proportional counters have many internal wires and electrodes and are called multi-wire proportional counters or simply MWPCs. Radiation detectors have also been used extensively in nuclear physics, medicine, particle physics, astronomy and in industry.

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Recipea Put a radioactive source in a holder. Fix this in a clamp on a retort stand.

b Put the Geiger-Mller tube in a stand. Adjust it so that it is pointing at the source, and is about 6 cm away from it.

c Plug the Geiger-Mller tube into the scaler (counter) and switch on. d Start the voltage at about 300 volts. Make a note of the number of counts in, say, a 60 second interval. e Increase the voltage in steps of 20 volts. f You will find that the counts vary with voltage and then reach a plateau. A graph would look like this (you do not need to plot the graph):

g After the threshold voltage, the count will reach a plateau. It will stay constant over a range of voltages. Set the voltage at a value of between 50 to 100 V above the threshold. h If the clicking increases when you increase the voltage, then you have moved off the plateau. Turn the voltage back down. i Put the source back in a safe place until you carry out the demonstration. Carrying out the demonstration a Switch on the Geiger-Mller tube counting system. b Highlight the fact that there is a background count. c Bring a radioactive source up to the Geiger-Mller tube and draw attention to the increase in counts.

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Observations

Obs. No. 32041

Voltage (V) 300

Activity (cpm) 0

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2 3 4 5 6 7 8 9 10

Sr. # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Time(min) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Activity(Cpm) 935 745 534 452 359 291 250 193 204 160 157 130 132 109 110

ln(A) 6.84 6.61 6.28 6.11 5.88 5.67 5.52 5.26 5.31 5.07 5.05 4.86 4.88 4.69 4.70

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