ADVANCED LAB PHY 4822L
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KA6759 Light emitting diodes for determining h 34 32 460 42 43 44 45 46 TV 75333 Leuchtdioden In Wellenl nge 480 nm ZOMAW 560 nm somW 0590 um y 0635 um l Introduction The physics of light emitting diodes Technical data Experiments Determination of the wavelength with a diffraction grating subjective image of the light emitting diode Diffraction at a grating in the visible range with real images of the light emitting diode Diffraction at a grating with infrared light The relationship between luminous intensity and current magnitude Currentvoltage characteristics of light emitting diodes Estimation of Planck39s action quantum References KLINGER EDUCATIONAL 1quot PRODUCTS CORP 112 19 14m ROAD COLLEGE POINT NEW YORK 11356 718 4611822 ELWE Lehrsysteme GmbH Light emitting diodes for determining h 84 82 460 1 Introduction Light emitting diodes can be used not only for classical experiments in optics such as wave length determination but also for experiments relating to thequantum nature of light By this simple means an estimate of the value of Planck39s action quantum canbe obtained The demonstration of the linear relationship between the photon energy E and the light fre quency f is possible with greater accuracy than when using a vacuum photoelectric cell In addi tion to the photoelectric effect Xray bremsstrahlung and Compton scattering this experiment constitutes another example of the quantum nature of light 2 The ghysics of light emitting diodes The phenomenon of light generation by electric excitation of a solid body was rst observed by HJRound 1 in 1907 on silicon carbide SiC OVLossew 2 who further investigated this electroluminescent effect during the years 1927 to 1942 already assumed correctly that this is the inverse process with respect to the photoelectric effect discovered by Einstein A more de tailed explanation of the actual mechanism namely the radiating recombination of minority carri ers injected across a pnjunction was given much later by K Lehovec in 1951 3 Indepen dently thereof in 1935 G Destriau 4 found a similar luminous effect known by his name when he applied an electric eld to zinc sul de crystallites However the excitation mechanism of this effect differs from that of the injection luminescence found with SiC The electro luminescence of ZnS was further developed for technical exploitation in the 19505 Whereas no success was achieved here the Ill V compounds recognized to be semiconductors by HWelker 5 in 1951 brought the desired technical break through These semiconductors consisting of one atom each from the third and the fth column of the periodic system of the elements have some remarkable properties which distinguish them from the classical semi conductors silicon Si and germanium Ge First of all they have a wide spectrum with some band separations Eg much greater than those of Si and Ge so that their equivalent frequencies f E h extend into the visible spectral range Furthermore some of these semiconductors have much greater ef ciency fac tors for radiating recombination of electrons and holes and in some cases also much greater charge carrier mobilities than Ga and Si Their complicated technology which was mastered for technical massproduction not before the end of the 1960s is the chief reason why these Ill V semiconductors are used today only where the abovementioned advan tages over Si and Ge dominate For luminescent and laser diodes and for highest speed devices Luminescent light emitting diodes operate according to the principle of injection luminescence ie they are simple pndiodes in which with current polarity in the forward direction some of the charge carriers injected into the neutral n and pregion recombine radiatively thereby emitting a photon with energy 5 h rlt E Q ELWE Lehrsysteme GmbH Light emitting diodes for determining h 84 82 460 The kind of doping involved here coinsists of so called isoelectronic lattice defects In these po sitions of the crystal lattice the atom which replaces the normal one comes from the same co lumn of the periodic system of the elements ie in contrast to the case with normal donors and acceptors these lattice defects make no contribution to the charge carrier balance in the semi conductor But they differ so greatly from the substituted atom with regard to atomic radius and electronegativity that charge carriers can be bound The best known isoelectric lattice defect in GaAsP consists of a nitrogen atom in the place of an arsenic or phosphorus atom On account of its smaller atomic radius and its greater electronegativity such a nitrogen atom can bind an electron By Coulomb interaction this in turn binds a hole The bound electron and hole consti tute a socalled bound exciton A photon is emitted when this exciton decays ie when the be und electron and hole recom bine The advantage of these isoelectric lattice defects lies in the strong localization of the primarily bound electron As a result of the Heisenberg uncertainty principle this leads to a strong increase of the momentum uncer tainty of the electron and thus to the desired boost of the probability for radiating recombination 3 Technical data Limiting data IR red Superred yellow green blue Inverse bias voltage 4 5 5 5 5 1 Fonivard current 100 75 50 50 50 25 Characteristic data Wavelength 950i20 665i15 635115 59015 56015 480140 nm Aperture cone 10 deg 12 deg 12 deg 12 deg 12 deg 16 deg Composition GaAsSi GaAsQ35 Po65N GaPzN SiC GaAsovs F O394 GaAs m5 PO SszN 500 540 580 620 660 rap nm wavelength Fig4 Relative spectral emission curves ELWE Lehrsysteme GmbH Light emitting diodes for determining h 84 82 450 important note Connect the power supply voltage to the light emitting diodes only via the builtin series resistor 100 Ohms 4 Experiments 41 Determination of the wavelength with a diffraction at a grating virtual image of the light emitting diode The selected LEDs in the NEVA collection of light emitting diodes are well suited for subjective observation of diffraction at a grating No3942 with 25 lines per mm by virtue of their predo minant radiation in the forward direction and resulting high luminous intensity The beam must be restricted by a slit width lt 1 mm because the coloured plastic body of the chosen diodes radiates light from its entire surface Measure the distance delta of the virtual images from the symmetry axis After setting a known distance D eg 1 m between the ruler and the diffraction grating determine by quick change of view through the grating or directly on the ruler at what distance delta a maximum of highest possible order k appears to lie The wavelength is then calculated according to the equation lambda sin arctandeltaD dk where d is the diffraction grating constant 42 Diffraction at a grating in the visible range with real images of the light emitting diode The light emitting diodes with the colours green yellow and super red have suf cient luminous intensity for generating real diffraction images with diffraction gratings in a darkened room The beam must be restricted with a slit as described in Section 41Fig5 shows the basic setup for this experiment The optical components used here can be taken from the pupil exercise equip ments 0013 Optics and 3901 Wave Optics Lens 1 L2 l I ae ici I quot f 39 iv 897 A l 3939 quot quott 39 r y 0 Lquot l 2 l G Fig5 Diagram of ray paths for diffraction with LED at diffaction grating ELWE Lehrsysteme GmbH Light emitting diodes for determining h 84 82 460 Evaluate using the equation given in Section 41 43 Diffraction qratinq with infrared light Diffraction of infra red light at a grating can be demonstrated with the experimental set up shown in Fig6 700 Q 70k 1 Fig6 Experimental setup for diffraction of infrared light In this experiment the light emitting diode is operated with pulsating direct current 8 V from the Universal Transformer 5200 The output voltage of the photo transistor is further ampli ed by an operational ampli er and then indicated by an AC voltmeter Adjust before the actual measu rement using a LED which emits visible light reduce the power supply voltage to 6 V The use of alternating light reduces the disturbing effect of ambient illumination so that only moderate darkening of the room is necessary in order to be able to carry out this experiment 44 The relationship between luminous intensity and current magnitude As a preliminary experiment before subsequent determination of h it is useful to observe quali tatively that on gradually increasing the voltage applied to the diode emission of lightcommen ces at the same point at which electric current starts to flow This observation indicates a causal relationship between these two physical quantities 45 Currentvoltage characteristics of light emitting diodes Fig7 shows the currentvoltage characteristics of all 6 light emitting diodes in one diagram An XY chart recorder was used to draw this diagram The voltage drop across the builtin 100 Ohm resistor was used as measured signal for the vertical axis ELWE Lehrsysteme GmbH Light emitting diodes for determining h 84 82 460 l r I mA p R 60 Japan 50 red green 40 yellow 30 blue 20 70 F l v i t U v 7 2 3 Fig TUIV The diffusion voltages UD are obtained approximately by linear extrapolation of the currentvoltage curves to their points of intersection with the voltage axis Uaxis 46 imation of Planck39s action uantum Fig8 shows a plot of the measured values of the diffusion voltages as a function of the frequency f l 3 UUV A A l o 2 z 6 r 10 4 Hz Fig8 The relationship between the diffusion voltage UD and the frequency f The best straight line through the measured points has been drawn on this diagram According to the explanations given in Section 2 the slope of this line should be We deltaUD deltaf ELWE LehrsySteme GmbH Light emitting diodes for determining h 84 82 460 The resulting measured value for We is 5 3135101 vsi5 The error of t 5 was estimated from the accuracy with which UD can be determined A comparison with the value 41356 103915 V s in standard tables shows that there is a systematic deviation towards values which are too small The cause for this deviation lies in the use of the relationship eUDhf investigations of the dependence of the diffusion voltage UD on temperature and comparison with technical data books shows that UD increases as the temperature drops 1UDdeltaUDdeltaT 5 10 This rise can explain the systematic error observed at room temperature 5 References 1 Round HJ A Note on Carborundum Elektron World 149 308 309 1907 2 Lossew OV The Behaviour of Contact Detectors Russian TelegrafiaTelefonia 18 61 63 1923 3 Lehovec K GA Accardo and E Jamuschian Injected Light Emission of Silicon Carbide Crystals Phys Rev 83 603 1951 4 Destriau G Scintillation of Zinc Sulphide with XrRays J Chem Phys 33 587 588 1936 5 Welker H New Compounds with Semiconductor Properties Z Naturf 7 a 744 749 1952 and 8 a 248 1958 General literature on semiconductors and light emitting diodes Bergh A A and P J Dean Light Emitting Diodes Oxford Clarendon Press 1976 Bleicher M Semiconductor OptoElectronics Heidelberg Huethig 1975 Seeger K Semiconductor Physics Vienna New York Springer Verlag 1976 Winstel G and C Weyrich OptoElectronics l Luminescent and Laser Diodes Berlin Springer Verlag 1980 User s Manual PLANCK S CONSTANT APPARATUS Model PCA01 MOODY INTERNATIONAL ISO 9001 2000 Certified Company Authorised reseller and service providers in North America SVS Labs Inc 12262 Goleta Avenue Suite 210 Saratoga CA 95070 USA Phone 14082309381 Fax 14085170557 email infosvslabscom website wwwsvsiabscom Manufactured by Scientific Equipment amp Services 3581 New Adarsh Nagar Roorkee 247 667 UA INDIA Ph 911332272852 277118 Fax 9 l1332274831 Email sessestechnocom Website www5estechnocom DETERMINATION OF PLANCK S CONSTANT FROM THE LED INTRODUCTION The Planck s constant is one of the universal constants which a student comes across quite early It is one of the basic ingredients of quantum physics Its measurement naturally has to be 39part of any collegeuniversity physics laboratory program Traditional method of measurement has been a determination of current cutoff voltage of a vacuum photocell irradiated by a monochromatic source of light Vacuum photocells are not easily available now and a reasonably strong source of monochromatic light is also dif cult to maintain in an undergraduate laboratory An alternative method is however available It employs light emitting diodes LEDs which are widely used in various consumer products and are easily available Most LEDs are based on GaAs and GaP crystals with general composition GaAsLX P where the fraction x varies between 0 and 1 These materials are direct semiconductors The crystals are doped with small amounts of different impurities in adjacent regions to form a PN junction or diode These doped crystals emit light when a voltage is applied across the junction The colour of the emitted light depends on the exact value of x THEORY The basic idea in this measurement is that the photon energy which from Einstein s relation is l3y hv is equal to the energy gap Eg between the valence and the conduction bands of the diode The gap energy Eg is in turn equal to the height of the energy barrier eV0 that the electrons have to overcome to go from the n doped side of the diode junction to the pdoped side when no external voltage V is applied to the diode In the pdoped side they recombine with the holes releasing the energy Eg as photons with E Eg eVo Thus a measurement of V0 indirectly yields E and the Planck s constant if v is known or measured However there are practical and conceptual problems in the actual measurement Let us consider the LED diode lV equation 1 oc exp VoVt exp VVt l V Vm RI 1 where Vt nkTe k T and e are Boltzmann constant absolute temperature and electronic charge respectively Vm is the voltmeter reading in the external diode circuit and R is the contact resistance The constant T is the material constant which depends on the type of diode location of the recombination region etc The energy barrier eV0 is equal to the gap energy Eg when no external voltage V is applied as pointed out earlier The quantities which are constant in an LED are the impurity atom density the charge diffusion properties and the effective diode area The one in the rectifier equation is negligible if I 2 2 nA and the equation becomes 1 0c exp vvovtn oc exp eVVon kT 2 A direct method could be to apply a small voltage on the LED and increasing it till the LED is tumedon This tuming on could be detected by visually observing the light emission Plotting threshold voltage vs frequency of peak light output obtained from LED catasheets or from separate spectroscopic measurement provides the value of 116 The visual observation of the emission on set is quite vague Use of a photo multiplier is sometimes suggested for this purpose but working with it raises maintenance problems and is quite costly Altemately a measurement of threshold current lt 10 A through the LED may be attempted but it is dif cult and not entirely accurate due to inef ciencies of actual LED s Another procedure some times used is to draw a tangent to the IV characteristics of the diode and obtain its intercept This procedure may give reasonable good results if the tangents to the I V characteristics of all the diodes are drawn at the same current The method then really becomes equivalent to measuring voltage across the LED s at a single current all the LED s of the set are connected in series The intercepts of the tangents are except for an additive constant identical to diode voltages The additive constant may be eliminated by considering data from different LED s However the bulk of data collected from the original IV graph becomes irrelevant A basic drawback of these methods is the assumption that the barrier height V0 is constant equal to the gap energy Eg divided by the electronic charge Ege which is true only when the external potential V is small or atleast less Ege They further assume that the material constant 11 is unity which is not correct It may have any value from about one to about two varying from LED to LED The present method is free from these in rmities The height of the potential barrier is obtained by directly measuring the dependence of the diode current on the temperature keeping the applied voltage and thus the height of the barrier xed The external voltage is kept Xed at a value lower than the barrier The idea is that the disturbance to the potential barrier is as little as possible I In our experimental setup the variation of the current I with temperature is measured over about a range of about 30 C at a xed applied voltage V z 18 volts kept slightly below V0 The slope of lnI vs lT curve gives 6 V0 Vnk Fig1 The constant 11 may be determined separately from I V characteristic of the diode Fig2 at room temperature from the relation 1 ekTAVA lnI 3 The Planck s constant is then obtained by the relation heV0 Me 4 The contact resistance of the LED is usually around 1 ohm while overall internal resistance of the LED at applied voltage z 18 V is few hundred ohms The factor RI in expression V Vm RI may therefore be neglected The value of Planck s constant obtained from this method is within 5 of accepted value 662 x 103934 Joulessec EXPERIMENTAL SETUP E39l 39I39U 1n I I39mw u 0 y The setup consists of the following units 1 To draw IV characteristics of LED i Variable voltage source 0 Range 0195 V Variable Resolution lmv 0 Accuracy i 02 0 Display 312 digit LED DPM ii Current Meter 0 Range 2 02000 pA 0 Resolution 1 pA 0 Accuracy l 02 0 Display 312 digit LED DPM 2 Dependence of current I on temp T at constant applied voltage i Current Meter 0 Range 020 mA 0 Resolution 10 pA 0 Display 312 digit LED DPM ii Temperature Controlled Oven Range Ambient to 65 C 0 Resolution 01 C 0 Stability l 02 C 0 Display 312 digit LED DPM iii Variable Voltage source of lst section is used to apply a constant voltage DESCRIPTION OF APPARATUS v quotJ V 3 MAINS ONOFF SWITCH To switch On Off the instrument VOLTAGE ADJ KNOB To adjust voltage VOLTAGETEMPERATURE DPM Read voltage in V l mode and temperature of oven in Tl mode 4 V LED SOCKET To connect LED samples 5 CURRENT DPM Display current in uA in Vl mode and in mA in Tl mode 6 Vl Tl SWITCH A two way switch to switch the system between V l mode and Tl mode 7 V a TEMPERATURE CONTROLLER ONOFF Switch for oven b OVEN Socket on the panel is to connect the external oven 0 d SETTEMP Knob to set the temperature OVEN It is a small oven with built in RTD sensor PROCEDURE 1 To draw IV characteristic of LED 0 ii iii Connect the LED in the socket and switch ON the power Switch the 2way switch to V I position In this position the 1st DPM would read voltage across LED and 2nd DPM would read current passing through the LED Increase the voltage gradually and tabulate the VI reading Please note there would be no current till about 15 V Draw the graph lnl I in uA Vs V 2 Dependence of current I on temperature T at constant applied voltage i ii iii iv Keep the mode switch to V l side and adjust the voltage across LED slightly below the bandgap of LED say 18 V for YellowRed LED and 195 for Green LED Switch the MODE switch to T I side Insert the LED in the oven and connect the oven to the socket Please make sure before connecting the oven that oven switch is in OFF position and SET TEMP knob is at minimum39 position Now the DPM would read ambient temperature Set the different temperatures with the help of SETTEMP Allow about 5 minutes time on each setting for the temperature to stabilize and take the readings of temperature and current Draw the graph lnl vs lT PRECAUTIONS l Vl characteristics of LED should be drawn at very low current upto E 1000 uA only so that the disturbance to V0 is minimum quot In Tl mode make sure that the oven switch is OFF and SET TEMP knob is at minimum position before connecting the oven 3 On each setting of temperature please allow suf cient time for the temperature to stabilize normally 56 minute is required 4 Though temperature of oven may go upto 70 C it is recommended that reading may be taken upto 60 C only to avoid excessive heating of LED 5 In case the LED is replaced please note that height of the portion inside the oven should not be more than 26mm otherwise it may strike the RTD REFERENCES l R Morehouse Am J Phys 1998 12 2 F Herrmann and D Sch citzle Am J Phys 63 1996 1448 3 LL Nieves The Physics Teacher 35 1996 108 u TYPICAL RESULTS EXPERIMENT 1 Determination of Material Constant n Sample Yellow LED Room Temperature 305K S No Junction Voltage V Forward Current I In 1 in Volts in pA 1 1604 e 40 369 2 1629 70 425 3 1644 100 461 4 1676 200 530 5 1711 405 600 6 1743 734 660 7 1765 1040 695 lV Characteristics 75 Sample LED Yellow Ambient Temp T 305K 65 39 Alnl 25 In I U1 U1 I 45 35 1 4 16 18 2 Junction Voltage V Graph no 1 From graph no 1 Junction Voltage Vvs lnI we get AV quot0124v lnl 25 Slope of the curve Therefore T1 n189 eAV LXPERIMEN T 11 Determination of Temperature Coef cient of Current Sample 39 Yellow LED 1602gtlt1019 x 0124 kT Aln11381gtlt10 23 x305x25 V 1805 V Constant for whole set of readings S No Temperature Temperature Current 1T X 10393 In C K mA Kquot 1 in mA 1 320 3050 185 328 062 2 345 3075 200 325 069 3 400 3130 225 319 081 4 454 3184 249 314 091 5 503 3233 271 309 100 6 553 3283 297 305 109 7 616 3346 334 299 121 Tl Characteristics 13 1 2 Sample LED Yellow 39 V1805V 11 1 A 1 052 E 09 Aquot E 08 a 07 06 05 04 39 39 L P 39 28 29 3 31 32 33 34 35 T 1X104 Graph N0 2 From Graph No 2 IT vs In Alnl 052V Slope of the curve 3 A3 AT x 10 026 x10 AlnI k v v ATquotgtlt10393 e n 052 1381x103923 026x10 1602x10 0 1805 o 1805 20 x103x 0862 x 10394 x 189 V39o 1805 0326 V0 213 eV 2 2 5800A as measured by diffraction grating tum ex Voxl 1602gtltIOA19 x213gtlt5800gtlt10quot3 h c 3gtlt1010 h 660 x 103934 Joules sec v 39 W39 T 7 MTV A v w LIMITED 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and effect y r Physics Chemistry Biology Technology 0605W97Sel 1 Description The Helmholtz pair of coils is intended for use on the tube stand 555 600 and adapted to the dimensions of the LD demonstration tubes 555 610 ff During arrangement in the distance which is marked on the tube stand with H an ap proximately homogeneous magnetic field is produced 2 Scope of supply 2 coils on support with stand rod 2 magnetic feet 3 Technical data Technical data of one coil Max current load 2 A DC resistance 6 Q 320 4 mm safety sockets 130 mm x 10 mm Number of turns Connections Stand rod Mean coil diameter 134 cm Helm holtz arrangem ent Mean coils distance 67 cm B 425 mT Magnetic induction B current through one coil Lehr und Didaktiksysteme LD Didactic GmbH Leyboldstrasse 1 D50354 Huerth Instruction sheet 555 604 Helmholtz pair of coils 555 604 A Connection to beginning of coil E Connection to end of coil 4 Helmholtz arrangement Arrange the coils in such a way that the connection sockets point outward For parallel connection connect the sockets A and E of coil 1 with the sockets E and A of coil 2 respectively and to a DC voltage source 0 l2 V 4 A For series connection connect socket E of coil 1 with socket E of coil 2 and the sockets A of both coils to a DV voltage source 024 V 2 A LD Didactic GmbH Leyboldstrasse1 D50354 HuerthGermany by LD Didactic GmbH Phone 02233 604 0 Fax02233604 222 email infoddidacticde Printed in the Federal Republic of Germany Technical alterations reserved 7 Scienti c Technical Training Education and Education Trade LEYBOLD DIDACTIC GmbH L E Y B O L D 0499V5Pr Instruction Sheet 586 850 Base Unit for Hall Effect 586 850 1 Output for Hall voltage 2 Current source crosscurrent adjuster 2a input for supply voltage 2b 3 Compensation onoff switch 3a compensation knob 3b Output for voltage drop at Ge crystal HEATER key with LED Temperature measuring output Power input for heating and electronics Mounting for plugin boards DIN socket 8a window 8b holes 8c 9 Rod with stop rumorh 1 Description The base unit for Hall effect is used to investigate the Hall effect An electronic compensation circuit can be activated to adjust and the electrical conductance of Ge crystals on plugin boards the zero point of the Hall voltage at room temperature for a se 586 851853 as a function of temperature It provides an adju lected cross current stable current source for the crosscurrent lthrough the Ge cry stal The device measures the Hall voltage UH resp the voltage The waveform laments used to heat the Ge crYStals on the dro39 Uat the Ge or stal 39 plugin boards are supplied by the base unit for Hall effect At p y 39 t e same time the deVIce outputs a voltage U3 proportional to For the Hall effect the devices is arranged between the p0e the crystal temperature 1 To protect the sensitive Ge crystals pieces of the demountable transformer 562 11 ff You can the heating automatically cuts out at 165 C measure the magnetic field in the immediate vicinity of the cry stal using the tangential Bprobe 516 60 Safety notes Electrostatic discharge ESD protection measures The sensitive electronics of the base unit for Hall effect can be When the base unit for Hall effect is used in expanded experi damaged or even destroyed by static electricity discharge ment setups in which connecting leads act as antennas Select your working environment so that no electrostatic SW19 39e tr magne e39d an interim With the function of Charging of the user andor the experiment equipment can the deVIce to theextent that it is temporarily unable to function occur no carpeting or similar implement electropotential adequately e39g39 39ncorreCt HaHVOItage39 bonding ground experimenter Keep all connecting leads as short as possible Make sure that no RF sources which are not part of the expe riment setup eg cellular telephones are in operation in the vicinity Seite 24 2 Technical data Mounting for plugin boards Connection DIN socket Outputs Hall voltage 2 safety sockets 4 mm Voltage dr p 0 across Ge crystal 2 safety sockets 4 mm Adjustable current source and UH compensation Power supply 12 V 50 mA DC Connection for power suppl safety sockets 4 mm Current range 2 mA to approx 32 mA Compensation voltage approx 35 mV at 32 mA 3 Operation 31 Mounting the plugin boards 586 8513 Instruction sheet 586 850 Heating and temperature measurement 15 V 3 A DC current stabilized or 12 V 3 A DC Connection for power supply2 safety sockets 4mm Temperature measuring output Power supply 2 safety sockets 4 mm 61000C i v Temperature calibration General data Dimensions without rod Rod Weight 275 mmgtlt 125 mmgtlt50 mm 50 mmgtlt10 mm dia 08 kg 32 Arrangement in a homogeneous magnetic field IIIIIIII O IIIIIIII O additionally required 1 Ge undoped on plugin board 586 851 or 1 pGe on plugin board 586 852 or 1 nGe on plugin board 586 853 Turn the plugin board so that the side with the crystal faces the front of the base unit Insert the plugin board with DIN plug into the DIN socket on the base unit until the pins latch into the holes additionally required 1 Ucore with yoke 562 11 1 Pair of bored pole pieces 560 31 2 Coils 250 turns 562 I3 Insert the base unit with rod into the hole of the Ucore all the 39 make sure that the plugin board is seated parallel to the Ucore Attach the pair of bored pole pieces with additional pole piece and slide the additional pole piece as far as the spacers of the plugin boards make sure that the plugin board is not bent E m lt P o F 3 m m P o 37 additionaly recommended for measuring the magnetic field 1 Tangential Bprobe 516 60 Instruction sheet 586 850 Seite 34 4 Carrying out the experiment 41 Measuring the Hall voltage as a function ofthe magnetic flux density the temperature or the crosscurrent only for p or ndoped Ge crystal 6 Experiment examples Set the crosscurrent lto the maximum value see Instruction Sheet for Ge crystal switch compensation on and zero the Hall voltage using the compensation knob a Vary the crosscurrent l Set the magnetic flux density B resp the current through the magnet coils vary the crosscurrent land measure the corre sponding Hall voltage UH b Varying the magnetic flux density B Vary the magnetic flux density B resp the current through the magnet coils and measure the corresponding Hall voltage UH c Varying the temperature 13 Set the magnetic flux density B resp the current through the magnet coils Press the HEATER key and record the Hall voltage UH as a function of voltage U0 at the temperature measuring output using CASSY or an XYrecorder additionally required 1 pGe on plugin board 586 852 or I nGe on plugin board 586 853 a Coil powersupply 1Powersupply 20 V 5 A DC eg 52150 optionally l ammeter I 5 A for coi current b Heating and electronics power supply 1 Power supply 15 V 3 A DC current regulated eg 521 50 or 1 Power supply 12 V 3A DC optionally l ammeter I 3 A c Supplying the controllable voltage source 1 Power supply 12 V 50 mA DC eg 521 54 optionally l ammeter I 50 mA for crosscurrent through Gecrystal d Temperature measuring output 1 Voltmeter U S 165 V e Measuring the Hall voltage 1 Voltmeter US 100 V 0 Measuring the magnetic eld 1 Tangential Bprobe 516 60 1 Bbox 524 038 or 1 Teslameter 516 62 Seite 44 Instruction sheet 586 850 42 Measuring conductivity as a function of temperature 586 850 Experiment examples a Variation of the crosscurrent l Vary the crosscurrent I see Instruction Sheet for Ge crystal and measure the voltage drop U c Varying the temperature 13 Set the crosscurrent lsee Instruction Sheet for Ge crystal press the HEATER key and measure the voltage drop Uas a function of the voltage U0 at the temperature output using CASSY or an XYrecorder additionally required 1 Ge undoped on plugin board 586 351 or I pGe on plugin board 586 852 or I nGe on plugin board 586 853 a Heating and electronics power suppy39 1 Power supply 15 V 3 A DC current regulated eg 521 50 or 1 Power supply 12 V 3A DC optionally I ammeter I S 3 A b Supplying the controllable voltage source I Powersupply12 V 50 mA DC eg 521 54 optionally I ammeter I S 50 mA for crosscurrent through Gecrysta c Temperature measuring output I Voltmeter U S 165 V d Measuring the voltage drop at the Ge crystal 1 Voltmeter U S 3 V LEYBOLD DIDACTIC GMBH Leyboldstrassel D750354Hurth Phone 02233 60470 Telefax 02233 6047222 email inf0leyboldrdidacticde by Leybold Didactic GmbH Printed in the Federal Republic of Germany echnical alterations reserved
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