Fri December 23, 2011 By: Siddhartha Basuroy

can the potential across a pn junction be measured using a standard voltmeter?

Expert Reply
Sun December 25, 2011
The built-in voltage of a PN junction can be considered as the contact potential between two dissimilar metals. When the leads of a voltmeter are contacted to either side of a PN junction, the contact potential between the voltmeter lead and P-type material, contact potential of the PN junction, and the contact potential between the N-type material and the voltmeter lead form a closed loop. Since the sum of all contact potentials in a closed loop is zero, the built-in voltage can not be measured by a voltmeter.
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