{"id":184,"date":"2009-07-27T06:18:19","date_gmt":"2009-07-27T11:18:19","guid":{"rendered":"http:\/\/www.blueraja.com\/blog2\/?p=184"},"modified":"2011-05-03T11:45:33","modified_gmt":"2011-05-03T16:45:33","slug":"whats-the-difference-between-voltage-at-a-point-and-voltage-between-two-points-also-what-is-ground","status":"publish","type":"post","link":"https:\/\/www.blueraja.com\/blog\/184\/whats-the-difference-between-voltage-at-a-point-and-voltage-between-two-points-also-what-is-ground","title":{"rendered":"What’s the difference between “voltage at a point” and “voltage between two points?” Also, what is ‘ground?’"},"content":{"rendered":"

Voltage is a measurement of the (potential) force driving electrons between two points, and is always a relative measurement. For instance, if I said "it’s 30 degrees in here,"<\/em> that would be an absolute measurement of temperature. However, if I said "it’s 5 degrees colder in here than in the kitchen,"<\/em> that’s a relative measurement between here and the kitchen. Voltage is always relative ("absolute voltage" is called electric potential<\/em>).<\/p>\n

When discussing the voltage at a point in a circuit, we actually mean the voltage between that point and ground. Ground<\/em> is an arbitrary point in the circuit that we decide to call 0 volts, and measure the voltage in the rest of the circuit relative to. In DC circuits, ground is usually the negative terminal of the power supply\/battery. In AC circuits, ground refers to either neutral or a third connection aptly named ‘ground.’ See ‘What’s the difference between neutral and ground<\/a>‘ for more information.<\/em><\/p>\n

For example, when a battery states that it’s 9 volts, it really means the voltage between its two terminals is 9 volts. When people tell you wall outlets are 120 volts (220 in Europe), they mean the voltage between the left- and right-plugs is 120 volts*. If a circuit diagram states a point in the circuit is 0 volts, it means that point and the negative terminal have the same electric potential (and are probably directly connected to one-another).<\/p>\n

*Since voltage is a wave in AC circuits and therefore changes (quickly) over time, 120 volts actually refers to a kind of average voltage<\/a> over time<\/p>\n","protected":false},"excerpt":{"rendered":"

Voltage is a measurement of the (potential) force driving electrons between two points, and is always a relative measurement. For instance, if I said "it’s 30 degrees in here," that would be an absolute measurement of temperature. However, if I said "it’s 5 degrees colder in here than in the kitchen," that’s a relative measurement […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/posts\/184"}],"collection":[{"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/comments?post=184"}],"version-history":[{"count":5,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/posts\/184\/revisions"}],"predecessor-version":[{"id":241,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/posts\/184\/revisions\/241"}],"wp:attachment":[{"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/media?parent=184"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/categories?post=184"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.blueraja.com\/blog\/wp-json\/wp\/v2\/tags?post=184"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}