{"id":316,"date":"2022-11-09T03:31:29","date_gmt":"2022-11-09T03:31:29","guid":{"rendered":"https:\/\/successrouter.com\/articles\/?p=316"},"modified":"2022-11-09T03:31:31","modified_gmt":"2022-11-09T03:31:31","slug":"absolute-pressure-and-gauge-pressure","status":"publish","type":"post","link":"https:\/\/successrouter.com\/articles\/absolute-pressure-and-gauge-pressure\/","title":{"rendered":"Absolute pressure and gauge pressure"},"content":{"rendered":"<h2 class=\"simpletoc-title\">Table of Contents<\/h2>\n<ul class=\"simpletoc-list\">\n<li><a href=\"#atmospheric-pressure\">Atmospheric pressure<\/a><\/li>\n<li><a href=\"#mercury-barometer-for-measuring-atmospheric-pressure\">Mercury barometer for measuring atmospheric pressure<\/a>\n<ul><li>\n<a href=\"#torricellis-experiment-of-measuring-atmospheric-pressure%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0\">Torricelli&#8217;s experiment of measuring atmospheric pressure.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/a><\/li>\n<li><a href=\"#mercury-barometer\">Mercury barometer<\/a><\/li>\n<\/ul>\n<\/li>\n<li><a href=\"#measurement-of-pressure-of-a-gas-using-open-tube-manometer\">Measurement of pressure of a gas using open tube manometer<\/a><\/li>\n<li><a href=\"#absolute-pressure-and-gauge-pressure\">Absolute pressure and gauge pressure<\/a><\/li><\/ul>\n\n<h3 class=\"wp-block-heading\" id=\"atmospheric-pressure\">Atmospheric pressure<\/h3>\n\n\n<p>The gaseous envelope surrounding the earth is called the atmosphere. The pressure exerted by the atmosphere is called atmospheric pressure. <\/p>\n\n\n\n<p>The force exerted by air column of air on a unit area of the earth&#8217;s surface is equal to the atmospheric pressure. The atmospheric pressure at sea level is 1.013 \u00d7 10<sup>5<\/sup> Nm<sup>-2<\/sup> or Pa.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"mercury-barometer-for-measuring-atmospheric-pressure\">Mercury barometer for measuring atmospheric pressure<\/h3>\n\n<h4 class=\"wp-block-heading\" id=\"torricellis-experiment-of-measuring-atmospheric-pressure%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0%25c2%25a0\">Torricelli&#8217;s experiment of measuring atmospheric pressure.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/h4>\n\n<h4 class=\"wp-block-heading\" id=\"mercury-barometer\">Mercury barometer<\/h4>\n\n\n<p>An Italian scientist E. Torricelli was first to device a method for measuring atmospheric pressure accurately. It is called a simple barometer. Aim long glass tube closed at one end is filled with clean and dry mercury. After closing the end of the tube with the thumb, the tube is inverted into a dish of mercury. As the thumb is removed, the mercury level in the tube falls down a little and comes to rest at a vertical height of 76 cm above the mercury level in the dish.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"198\" height=\"162\" src=\"https:\/\/successrouter.com\/articles\/wp-content\/uploads\/2022\/11\/image-6.png\" alt=\"\" class=\"wp-image-317\"\/><figcaption><strong>Fig. Mercury barometer.<\/strong><\/figcaption><\/figure><\/div>\n\n\n<p>The space above mercury in the tube is almost a perfect vacuum and is called Torricellian vacuum. Therefore, pressure P<sub>A<\/sub> =0. Consider a point C on the mercury surface in the dish and point B in the tube at the same horizontal level. Then<\/p>\n\n\n\n<p>P<sub>B<\/sub> = P<sub>C<\/sub> = Atmospheric pressure, P<sub>a<\/sub><\/p>\n\n\n\n<p>If h is the height of mercury column and \u03c1 is. the density of mercury, then<\/p>\n\n\n\n<p>P<sub>B<\/sub> = P<sub>A<\/sub>+h\u03c1g<\/p>\n\n\n\n<p>or&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; P<sub>a<\/sub> = 0 + h \u03c1 g<\/p>\n\n\n\n<p>or&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; P<sub>a<\/sub> = h \u03c1 g<\/p>\n\n\n\n<p>For a mercury barometer, h =76 cm =0.76 m, \u03c1 =13.6 \u00d7 10<sup>3<\/sup>kg m<sup>-3<\/sup>, g = 9.8 ms<sup>-2<\/sup>, therefore<\/p>\n\n\n\n<p>Atmospheric pressure,<\/p>\n\n\n\n<p>P<sub>a<\/sub> =0.76 \u00d7 13.6 \u00d7 10<sup>3<\/sup> \u00d7 9.8 =1.013 \u00d7 10<sup>5<\/sup> Pa.<\/p>\n\n\n<h3 class=\"wp-block-heading\" id=\"measurement-of-pressure-of-a-gas-using-open-tube-manometer\">Measurement of pressure of a gas using open tube manometer<\/h3>\n\n\n<p>Open-tube manometer. It is a simple device used to measure the pressure of a gas enclosed in a vessel. It consists of a Lf-tube containing some liquid. One end of the tube is open to the atmosphere and the other end is connected to the vessel.<\/p>\n\n\n\n<p>The total pressure P of the gas is equal to the pressure at A Thus<\/p>\n\n\n\n<p>P = P<sub>A <\/sub>= P<sub>C <\/sub>+ h \u03c1 g or P = P<sub>a<\/sub> + h \u03c1 g<\/p>\n\n\n\n<p>where P<sub>a<\/sub> is the atmospheric pressure, h = BC = difference in the levels of the liquid in the two arms and \u03c1 is the density of the liquid.<\/p>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"193\" height=\"198\" src=\"https:\/\/successrouter.com\/articles\/wp-content\/uploads\/2022\/11\/image-7.png\" alt=\"\" class=\"wp-image-318\"\/><figcaption><strong>Fig. Open tube manometer<\/strong><\/figcaption><\/figure><\/div>\n\n<h3 class=\"wp-block-heading\" id=\"absolute-pressure-and-gauge-pressure\">Absolute pressure and gauge pressure<\/h3>\n\n\n<p>Let&#8217;s discuss the differences between absolute and gauge pressure.<\/p>\n\n\n\n<p>The total or actual pressure P at a point is called absolute pressure. Gauge pressure is the difference between the actual pressure (or absolute pressure) at a point and the atmospheric pressure, i.e., P<sub>g<\/sub> = P &#8211; P<sub>a<\/sub> = h \u03c1 g<\/p>\n\n\n\n<p>The gauge pressure is proportional to h. Many pressure measuring devices directly measure the gauge pressure. These include the tyre pressure gauge and the blood pressure gauge (sphygmomanometer).<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Atmospheric pressure The gaseous envelope surrounding the earth is called the atmosphere. The pressure exerted by the atmosphere is called atmospheric pressure. The force exerted by air column of air on a unit area of the earth&#8217;s surface is equal to the atmospheric pressure. The atmospheric pressure at sea level is 1.013 \u00d7 105 Nm-2 &#8230; <a title=\"Absolute pressure and gauge pressure\" class=\"read-more\" href=\"https:\/\/successrouter.com\/articles\/absolute-pressure-and-gauge-pressure\/\" aria-label=\"More on Absolute pressure and gauge pressure\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[59,60,61,62],"_links":{"self":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/316"}],"collection":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/comments?post=316"}],"version-history":[{"count":1,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/316\/revisions"}],"predecessor-version":[{"id":319,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/posts\/316\/revisions\/319"}],"wp:attachment":[{"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/media?parent=316"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/categories?post=316"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/successrouter.com\/articles\/wp-json\/wp\/v2\/tags?post=316"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}