{"id":2117,"date":"2024-07-22T17:26:48","date_gmt":"2024-07-22T15:30:03","guid":{"rendered":"https:\/\/experiments.school\/?post_type=product&p=2117"},"modified":"2024-07-22T17:30:03","modified_gmt":"2024-07-22T15:30:03","slug":"018-thermocouple","status":"publish","type":"product","link":"https:\/\/experiments.school\/en\/product\/018-thermocouple\/","title":{"rendered":"018 – Thermocouple"},"content":{"rendered":"","protected":false},"excerpt":{"rendered":"

Thermoelectric effect\u00a0\u00a0<\/strong><\/h2>\n

Seebeck effect\u00a0\u00a0<\/strong><\/h2>\n

Generation of voltage by heating\u00a0<\/strong>\u00a0<\/span><\/h2>\n

 <\/p>\n

Introduction to:\u00a0<\/span>\u00a0<\/span><\/h2>\n
    \n
  • Thermometry\u00a0<\/span>\u00a0<\/span><\/li>\n
  • Electric thermometer\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n[video width=\"1920\" height=\"1080\" mp4=\"https:\/\/experiments.school\/wp-content\/uploads\/2024\/07\/018-video-end.mp4\"][\/video]\n

     <\/p>\n

    Material:\u00a0<\/span>\u00a0<\/span><\/h2>\n

    a)\u00a0<\/span><\/p>\n

      \n
    • Electrode for welding, made of nickel (the coating must first be removed using pliers and coarse sandpaper)\u00a0<\/span>\u00a0<\/span><\/li>\n
    • Copper wire (approx. 20 cm)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

      Contact voltage 20 \u03bcV\/K\u00a0<\/span>\u00a0<\/span><\/p>\n

      or<\/span><\/p>\n

      b)\u00a0<\/span><\/p>\n

        \n
      • Constantan wire (length approx. 20 cm; diameter approx. 0.5 mm)\u00a0<\/span>\u00a0<\/span><\/li>\n
      • Iron wire (length approx. 20 cm; diameter approx. 0.5 mm)\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

        Contact voltage 43 \u03bcV\/K\u00a0<\/span>\u00a0<\/span><\/p>\n

        or<\/span><\/p>\n

        c)\u00a0<\/span><\/p>\n

          \n
        • Nickel-chromium wire (length approx. 20 cm; diameter approx. 0.5 mm)\u00a0<\/span>\u00a0<\/span><\/li>\n
        • Nickel wire (length approx. 20 cm; diameter approx. 0.5 mm)\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

          Contact voltage 40 \u03bcV\/K\u00a0<\/span>\u00a0<\/span><\/p>\n

          In general:<\/span>Pairs of wires of two different metals A and B, e.g. also iron and zinc, are suitable <\/span>\u00a0<\/span><\/p>\n

            \n
          • Voltage meter in the millivolt range \/ multimeter\u00a0<\/span>\u00a0<\/span><\/li>\n
          • Alligator Clips\u00a0<\/span>\u00a0<\/span><\/li>\n
          • Candle \/ Lighter\u00a0<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

            Setup:<\/span>\u00a0<\/span><\/h2>\n

            a)\u00a0<\/span><\/p>\n

              \n
            • Remove the insulation from the copper wire and wrap it around the nickel electrode once or twice, creating a firm bond between the metals.<\/span><\/li>\n<\/ul>\n

              b) c)\u00a0<\/span><\/p>\n

                \n
              • Twist the ends of the two wires over a length of 5 cm<\/span>\u00a0<\/span><\/li>\n
              • Connect the voltage meter to the free ends of metal A and metal B.<\/span><\/li>\n<\/ul>\n

                Execution:\u00a0<\/span>\u00a0<\/span><\/h2>\n
                  \n
                • Heat the contact point of the metals with the candle flame.<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

                  Observation:\u00a0<\/span>\u00a0<\/span><\/h2>\n
                    \n
                  • The voltage meter shows a contact voltage in the millivolt range.<\/span><\/li>\n
                  • As the contact point heats up, the contact voltage increases.<\/span><\/li>\n
                  • For the metal pair a) copper \u2013 nickel it is : 20 \u03bcV\/K, i.e. 2 mV corresponds to a temperature increase of 100 K.<\/span>\u00a0<\/span><\/li>\n
                  • When cooling, the contact voltage decreases.<\/span>\u00a0<\/span><\/li>\n<\/ul>\n

                    Explication:\u00a0<\/span>\u00a0<\/span><\/h2>\n
                      \n
                    • The contact voltage is due to the different exit work of electrons from different metals, the Fermi levels are of different heights.<\/span><\/li>\n
                    • The contact voltage increases in proportion to the (absolute) temperature at the contact point.<\/span><\/li>\n<\/ul>\n

                      Tips:\u00a0<\/span>\u00a0<\/span><\/h2>\n
                        \n
                      • The contact between the metals can be increased by hitting the point of twisting with a hammer or soldering the wires together.<\/span>\u00a0<\/span><\/li>\n
                      • With a voltage meter in the \u03bcV range, even the heat of the hand can be detected.<\/span><\/li>\n
                      • In the metal pair metal A nickel-chromium – metal B nickel, the contact voltage is about 40 \u03bcV\/K (above 0 \u00b0C).<\/li>\n<\/ul>\n","protected":false},"featured_media":2119,"template":"","meta":[],"product_brand":[],"product_cat":[975,981,874,876,881],"product_tag":[],"class_list":{"0":"post-2117","1":"product","2":"type-product","3":"status-publish","4":"has-post-thumbnail","6":"product_cat-2-voltage-current","7":"product_cat-4-conductivity-resistance","8":"product_cat-b-electricity","9":"product_cat-d-thermodynamics","10":"product_cat-i-physical-devices","11":"","12":"woocommerce-text-align-left","13":"woocommerce-image-align-center","15":"first","16":"instock","17":"shipping-taxable","18":"product-type-simple"},"_links":{"self":[{"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/product\/2117","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/product"}],"about":[{"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/types\/product"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/media\/2119"}],"wp:attachment":[{"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/media?parent=2117"}],"wp:term":[{"taxonomy":"product_brand","embeddable":true,"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/product_brand?post=2117"},{"taxonomy":"product_cat","embeddable":true,"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/product_cat?post=2117"},{"taxonomy":"product_tag","embeddable":true,"href":"https:\/\/experiments.school\/en\/wp-json\/wp\/v2\/product_tag?post=2117"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}