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Ohm's law is not applicable to
DC circuits
high currents
small resistors
semi-conductors
semi-conductors
Ohm's law states that the current flowing through a conductor is directly proportional to the voltage applied across its ends, provided physical conditions like temperature remain constant. This linear relationship (V=IR) does not hold for devices such as semiconductors, vacuum tubes, or electrolyte solutions, which exhibit non-linear voltage-current characteristics.
Ohm's law states that the current flowing through a conductor is directly proportional to the voltage applied across its ends, provided physical conditions like temperature remain constant. This linear relationship (V=IR) does not hold for devices such as semiconductors, vacuum tubes, or electrolyte solutions, which exhibit non-linear voltage-current characteristics.
V=IR тАФ Ohm's Law (Linear)
I=I0тАЛ(ekTqVтАЛтИТ1) тАФ Shockley Diode Equation (Non-linear)
In metallic conductors, the carrier density and scattering mechanisms remain largely constant with applied voltage. In semiconductors, however, the charge carrier concentration is temperature-dependent and governed by the exponential barrier height in p-n junctions, resulting in a non-linear IтИТV curve that violates the linear assumption of Ohm's law.
Ohm's law is valid only for Ohmic conductors where the resistance is independent of the applied voltage.
Semiconductors like diodes and transistors have IтИТV characteristics that are exponential or logarithmic.
Non-ohmic devices do not maintain a constant ratio of V/I as the operating point changes.
Ohm's law is a limiting case and not a fundamental universal law of physics.
Simplicity in analyzing DC circuits
Predictable power dissipation in resistive loads
Cannot be used to model active components like transistors
Fails under varying temperature or high-frequency conditions
DC circuit analysis
Resistance measurement
Power system load flow studies
Option A: DC circuits are typically analyzed using Ohm's law.
Option B & C: These relate to practical limitations of the component's thermal capacity, not a violation of the fundamental principle of the material property.
A device is Ohmic if its V-I graph is a straight line passing through the origin.
D is correct тАФ Semiconductors are non-ohmic devices because their current-voltage relationship is non-linear and governed by junction physics rather than a constant resistance.
Always verify if a device is 'passive' or 'active' when considering Ohm's law applications; active devices like BJTs or MOSFETs are inherently non-ohmic.