Metals Al and Au are connected in series. An ideal voltmeter, with both of its leads made of Cu, is connected across them. Then how come the voltmeter gives zero reading but why can't we measure contact potential between them if there is potential difference electrons flow right then why electron flow can't be measured If so how can we prove on paper that it is 0 V

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    $\begingroup$ There are three junctions in your circuit: Au/Al, Al/Cu, Cu/Au. $\endgroup$ – Farcher Sep 14 at 8:19
  • $\begingroup$ I am interested in only between Al and Au you can consider only between them $\endgroup$ – YASHWANTH M Sep 14 at 8:44
  • $\begingroup$ That is fine for you to only consider one junction, but the voltmeter sees all three. It must see 0 volts, or you could connect Cu to Cu (no voltage) and have net voltage around a closed loop. $\endgroup$ – Jon Custer Sep 14 at 14:55
  • $\begingroup$ Ok consider all but how it is 0 it should measure contact potential right $\endgroup$ – YASHWANTH M Sep 14 at 17:56

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