Today we observed that the fully charged capacitor began to discharge immediately after being disconnected from the voltage source (batteries) prior to it being placed in the circuit with the ohmic resistor.\u00a0 The reason for this is that the BK DMM has its own internal resistance and therefore an RC circuit existed with the DMM and the capacitor.\u00a0 So be aware that sometimes measuring instrumentation can influence the value of what is being measured!<\/p>\n
It turns out that the internal resistance of the BK DMM when measuring voltage is 10M Ohm.\u00a0 This value is generally great enough to not influence voltage measurements.\u00a0 It certainly is fine for what we do in Lab.\u00a0 However an ideal volt meter should have infinite internal resistance. There are volt meters available with extremely high internal resistance, but as you might guess, these are much more expensive than our BK DMM’s.<\/p>\n
Given that the internal resistance of the BK Voltmeter is 10M Ohm, what is\u00a0\\(\\tau\\)<\/span> (without uncertainty) of the RC circuit consisting of just the DMM and the capacitor?<\/p>\n Background<\/a> Equipment<\/a> Data Collection and Analysis<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" Today we observed that the fully charged capacitor began to discharge immediately after being disconnected from the voltage source (batteries) prior to it being placed in the circuit with the ohmic resistor.\u00a0 The reason for this is that the BK DMM has its own internal resistance and therefore an RC circuit existed with the DMM […]<\/p>\n","protected":false},"author":293,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2070","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages\/2070","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/users\/293"}],"replies":[{"embeddable":true,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/comments?post=2070"}],"version-history":[{"count":0,"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/pages\/2070\/revisions"}],"wp:attachment":[{"href":"https:\/\/courses.bowdoin.edu\/physics-1140-lab-manual\/wp-json\/wp\/v2\/media?parent=2070"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}