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Failures of ohm's law

Failures of ohm's law

ohm's law is not a fundamental law .in many cases  it fails. 

Ohmic conductor: The conductor which obey ohm's law are called ohmic conductor.
eg. pure metals, cuso4 solution etc

for ohmic conductor;
1.V-I graph is straight line and passes through origin.
2. the direction of current is reverse, if P. D(V)  is reverse. but magnitude of I remains same.
3. for a potential difference,  there is only one value of current.
Non ohmic conductor: the conductors which do not obey ohm's law are called non ohmic conductors
eg. junction diode, water voltmeter, vaccum tube etc

for non ohmic conductor
1.graph B/w V&I is not straight line  i. e V/I not equal to constant.
2.if V-I graph is a straight line it does not passes through the origin. eg. water voltmeter.
3. current can have more value for a given potential difference i. e resistance does not have a constant value.
4.the relation B/w V-I depends upon the sign of V i. e currenthas different values of +V & -V.

V-I relationship is curve or non linear instead of straight line in case of lamp filament, junction diode, diode value and thermistor. etc



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