• Mangesh4438

MemberSep 23, 2011

## Ohm law

Ohm says i=v/r but at some condition current increases then voltage decreases how is that?
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Replies
• MemberSep 23, 2011

There are some electrical circuits which do not obey Ohm's law. For example, the p-n junction diode. In the p-n junction diode, current does not increase linearly with applied voltage. This happens because the value of "resistance" is not constant as a function of applied voltage. Further, the current only increases significantly if the applied voltage is positive, not negative.
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• MemberSep 23, 2011

Mangesh4438
Ohm says i=v/r but at some condition current increases then voltage decreases how is that?
check out the limitations of ohm's law....
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• MemberSep 23, 2011

may be the resistance decreases.. 😛 active devices such as transistors, diodes etc will not obey ohm's law
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• MemberSep 23, 2011

Mangesh4438
Ohm says i=v/r but at some condition current increases then voltage decreases how is that?
Source resistance. When load resistance decreases, current increases, and voltage drop at source side appears. For example:V battery= 14,4VR lamp = 4 OhmR starter = 0.144 OhmR internal of a battery= 0.024 OhmI1=Vbat/(Rlamp+Rbat)=3,57A Vlamp=Vbat-I1*Rbat=14.28VI2= Vbat/(Rstarter+Rbat)=85,7AVstarter= Vbat-I2*Rbat=12,34V
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• MemberSep 24, 2011

have you not ever come across varistors or non-linear resistors or lightening arrestors.
we can have material to follow ohm law only in the range we want by design and then can vary itsbehaviour with voltage.
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• MemberSep 25, 2011

Mangesh4438
Ohm says i=v/r but at some condition current increases then voltage decreases how is that?
If you are talking about real circuits the culprit may be the impedance of the source. The out put voltage of some power supplies could be higher when the load has a high resistance than when it has a low resistance. Ohm's law is still obeyed if one considers the total resistance, that is, source resistance plus load resistance.