Fréedericksz transition on air
10.1119/10.0003350.1 The operational principle of twisted nematic displays involves the dielectric anisotropy of nematics. This crucial property was discovered about a hundred years ago by Jeżewski and Kast who used a so-called resonance method in which the frequency of an LC tank circuit was set by...
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| Veröffentlicht in: | American journal of physics 2021-06, Vol.89 (6), p.603-611 |
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| container_title | American journal of physics |
| container_volume | 89 |
| creator | Plo, Juliette Sadi, Dihya Thellier, Elio Pieranski, Pawel Zeghal, Mehdi Judeinstein, Patrick |
| description | 10.1119/10.0003350.1
The operational principle of twisted nematic displays involves the dielectric anisotropy of nematics. This crucial property was discovered about a hundred years ago by Jeżewski and Kast who used a so-called resonance method in which the frequency of an LC tank circuit was set by the capacitance of a capacitor filled with a nematic liquid crystal. Jeżewski and Kast observed that the resonance frequency changed upon application of a magnetic field to the capacitor. They interpreted the corresponding change in the dielectric permittivity as being due to reorientation of molecules by the magnetic field. Here, we describe a modern, simple, and low-cost version of this experiment. Instead of the LC oscillator working with vacuum lamps, we use an op-amp RC oscillator in which a twisted nematic display plays the role of the capacitor. For the purpose of classroom demonstrations, the oscillator frequency fRC is detected by a software-defined radio operating in the double-side band mode (DSB). Upon an appropriate tuning of the reception frequency fo, even small changes of
Δ
f
=
f
R
C
−
f
o become audible. This setup is very convenient for demonstration and measurements of all characteristics of the Fréedericksz transition driven by magnetic or electric fields. |
| doi_str_mv | 10.1119/10.0003350 |
| format | Article |
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The operational principle of twisted nematic displays involves the dielectric anisotropy of nematics. This crucial property was discovered about a hundred years ago by Jeżewski and Kast who used a so-called resonance method in which the frequency of an LC tank circuit was set by the capacitance of a capacitor filled with a nematic liquid crystal. Jeżewski and Kast observed that the resonance frequency changed upon application of a magnetic field to the capacitor. They interpreted the corresponding change in the dielectric permittivity as being due to reorientation of molecules by the magnetic field. Here, we describe a modern, simple, and low-cost version of this experiment. Instead of the LC oscillator working with vacuum lamps, we use an op-amp RC oscillator in which a twisted nematic display plays the role of the capacitor. For the purpose of classroom demonstrations, the oscillator frequency fRC is detected by a software-defined radio operating in the double-side band mode (DSB). Upon an appropriate tuning of the reception frequency fo, even small changes of
Δ
f
=
f
R
C
−
f
o become audible. This setup is very convenient for demonstration and measurements of all characteristics of the Fréedericksz transition driven by magnetic or electric fields.</description><identifier>ISSN: 0002-9505</identifier><identifier>EISSN: 1943-2909</identifier><identifier>DOI: 10.1119/10.0003350</identifier><identifier>CODEN: AJPIAS</identifier><language>eng</language><publisher>Woodbury: American Institute of Physics</publisher><subject>Anisotropy ; Chemical Sciences ; Condensed Matter ; Cristallography ; Dielectrics ; Electric fields ; Magnetic fields ; Optics ; Physics ; Physics Education ; Resonance ; Soft Condensed Matter ; Statistical Mechanics</subject><ispartof>American journal of physics, 2021-06, Vol.89 (6), p.603-611</ispartof><rights>Author(s)</rights><rights>Copyright American Institute of Physics Jun 2021</rights><rights>Distributed under a Creative Commons Attribution 4.0 International License</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c467t-3bb139796a7889d7ddc6108bfd05979d2575b107a3156fc959eea274f7768c6e3</citedby><cites>FETCH-LOGICAL-c467t-3bb139796a7889d7ddc6108bfd05979d2575b107a3156fc959eea274f7768c6e3</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://pubs.aip.org/ajp/article-lookup/doi/10.1119/10.0003350$$EHTML$$P50$$Gscitation$$H</linktohtml><link.rule.ids>230,314,776,780,790,881,4498,27901,27902,76127</link.rule.ids><backlink>$$Uhttps://hal.science/hal-03234467$$DView record in HAL$$Hfree_for_read</backlink></links><search><creatorcontrib>Plo, Juliette</creatorcontrib><creatorcontrib>Sadi, Dihya</creatorcontrib><creatorcontrib>Thellier, Elio</creatorcontrib><creatorcontrib>Pieranski, Pawel</creatorcontrib><creatorcontrib>Zeghal, Mehdi</creatorcontrib><creatorcontrib>Judeinstein, Patrick</creatorcontrib><title>Fréedericksz transition on air</title><title>American journal of physics</title><description>10.1119/10.0003350.1
The operational principle of twisted nematic displays involves the dielectric anisotropy of nematics. This crucial property was discovered about a hundred years ago by Jeżewski and Kast who used a so-called resonance method in which the frequency of an LC tank circuit was set by the capacitance of a capacitor filled with a nematic liquid crystal. Jeżewski and Kast observed that the resonance frequency changed upon application of a magnetic field to the capacitor. They interpreted the corresponding change in the dielectric permittivity as being due to reorientation of molecules by the magnetic field. Here, we describe a modern, simple, and low-cost version of this experiment. Instead of the LC oscillator working with vacuum lamps, we use an op-amp RC oscillator in which a twisted nematic display plays the role of the capacitor. For the purpose of classroom demonstrations, the oscillator frequency fRC is detected by a software-defined radio operating in the double-side band mode (DSB). Upon an appropriate tuning of the reception frequency fo, even small changes of
Δ
f
=
f
R
C
−
f
o become audible. This setup is very convenient for demonstration and measurements of all characteristics of the Fréedericksz transition driven by magnetic or electric fields.</description><subject>Anisotropy</subject><subject>Chemical Sciences</subject><subject>Condensed Matter</subject><subject>Cristallography</subject><subject>Dielectrics</subject><subject>Electric fields</subject><subject>Magnetic fields</subject><subject>Optics</subject><subject>Physics</subject><subject>Physics Education</subject><subject>Resonance</subject><subject>Soft Condensed Matter</subject><subject>Statistical Mechanics</subject><issn>0002-9505</issn><issn>1943-2909</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2021</creationdate><recordtype>article</recordtype><recordid>eNqdkM1KAzEUhYMoOFY3voAFVyqjN8kkmSxLsVYYcKPrkEkymFo7NZkW7Bv5HL6YGaaIa-HC4R4-7s9B6BzDLcZY3iUFAEoZHKAMy4LmRII8RFlySS4ZsGN0EuMitRKXkKGLWfj-ctYFb97ibtwFvYq-8-1qnEr7cIqOGr2M7myvI_Qyu3-ezvPq6eFxOqlyU3DR5bSuMZVCci3KUlphreEYyrqxwJJtCROsxiA0xYw3RjLpnCaiaITgpeGOjtDVMPdVL9U6-HcdPlWrvZpPKtV7QAkt0q4tTuzlwK5D-7FxsVOLdhNW6TxFGOWMyhJIoq4HyoQ2xuCa37EYVB9Wr_uwEnwzwNH4Tvf__5PetuEPqda2oT-hLHUn</recordid><startdate>202106</startdate><enddate>202106</enddate><creator>Plo, Juliette</creator><creator>Sadi, Dihya</creator><creator>Thellier, Elio</creator><creator>Pieranski, Pawel</creator><creator>Zeghal, Mehdi</creator><creator>Judeinstein, Patrick</creator><general>American Institute of Physics</general><general>American Association of Physics Teachers</general><scope>AAYXX</scope><scope>CITATION</scope><scope>1XC</scope><scope>VOOES</scope></search><sort><creationdate>202106</creationdate><title>Fréedericksz transition on air</title><author>Plo, Juliette ; Sadi, Dihya ; Thellier, Elio ; Pieranski, Pawel ; Zeghal, Mehdi ; Judeinstein, Patrick</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c467t-3bb139796a7889d7ddc6108bfd05979d2575b107a3156fc959eea274f7768c6e3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2021</creationdate><topic>Anisotropy</topic><topic>Chemical Sciences</topic><topic>Condensed Matter</topic><topic>Cristallography</topic><topic>Dielectrics</topic><topic>Electric fields</topic><topic>Magnetic fields</topic><topic>Optics</topic><topic>Physics</topic><topic>Physics Education</topic><topic>Resonance</topic><topic>Soft Condensed Matter</topic><topic>Statistical Mechanics</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Plo, Juliette</creatorcontrib><creatorcontrib>Sadi, Dihya</creatorcontrib><creatorcontrib>Thellier, Elio</creatorcontrib><creatorcontrib>Pieranski, Pawel</creatorcontrib><creatorcontrib>Zeghal, Mehdi</creatorcontrib><creatorcontrib>Judeinstein, Patrick</creatorcontrib><collection>CrossRef</collection><collection>Hyper Article en Ligne (HAL)</collection><collection>Hyper Article en Ligne (HAL) (Open Access)</collection><jtitle>American journal of physics</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Plo, Juliette</au><au>Sadi, Dihya</au><au>Thellier, Elio</au><au>Pieranski, Pawel</au><au>Zeghal, Mehdi</au><au>Judeinstein, Patrick</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Fréedericksz transition on air</atitle><jtitle>American journal of physics</jtitle><date>2021-06</date><risdate>2021</risdate><volume>89</volume><issue>6</issue><spage>603</spage><epage>611</epage><pages>603-611</pages><issn>0002-9505</issn><eissn>1943-2909</eissn><coden>AJPIAS</coden><abstract>10.1119/10.0003350.1
The operational principle of twisted nematic displays involves the dielectric anisotropy of nematics. This crucial property was discovered about a hundred years ago by Jeżewski and Kast who used a so-called resonance method in which the frequency of an LC tank circuit was set by the capacitance of a capacitor filled with a nematic liquid crystal. Jeżewski and Kast observed that the resonance frequency changed upon application of a magnetic field to the capacitor. They interpreted the corresponding change in the dielectric permittivity as being due to reorientation of molecules by the magnetic field. Here, we describe a modern, simple, and low-cost version of this experiment. Instead of the LC oscillator working with vacuum lamps, we use an op-amp RC oscillator in which a twisted nematic display plays the role of the capacitor. For the purpose of classroom demonstrations, the oscillator frequency fRC is detected by a software-defined radio operating in the double-side band mode (DSB). Upon an appropriate tuning of the reception frequency fo, even small changes of
Δ
f
=
f
R
C
−
f
o become audible. This setup is very convenient for demonstration and measurements of all characteristics of the Fréedericksz transition driven by magnetic or electric fields.</abstract><cop>Woodbury</cop><pub>American Institute of Physics</pub><doi>10.1119/10.0003350</doi><tpages>9</tpages><oa>free_for_read</oa></addata></record> |
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| language | eng |
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| subjects | Anisotropy Chemical Sciences Condensed Matter Cristallography Dielectrics Electric fields Magnetic fields Optics Physics Physics Education Resonance Soft Condensed Matter Statistical Mechanics |
| title | Fréedericksz transition on air |
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