whether active device obeys ohms law?

Answer 1

Active devices are usually composed of semiconductors, which have PN junctions. PN junctions are not linear devices neither in forward or reverse bias, so they do not obey Ohms law.

Junction field effect transistors (FETs) have a region of operation where the source-to-drain acts like a resistor (obeys Ohms law).

Unijunction transistors and some tunnel diodes actally have a region of operation where there is aparent negative resistance (Ohms law with a negative slope).

Diodes in reverse bias up to the zener or avalanche point exhibit a very high resistance (due to leakage current), and it is fairly linear (Ohms law).

The above 3 examples are about the only ones among active devices where the device obeys Ohms law. Otherwise, active devices are generally non-linear.

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The above 2 examples are about the only ones

Answer 2

V will always equal I times R (Ohms law) in dc theory.

However in semiconductor devices the resistance may vary with voltage but as already stated V will always equal I times R (Ohms law).

Answer 3

If, regardless of the voltage you apply to the device, a constantly proportional amount of current is drawn, then the device is ohmic (following ohm's law).

In other words, if the I-V characteristics are a straight line, intersecting 0,0

Answer 4

resistors and thermistors. In AC circuits at steady state, coils and capacitors obey a variant of Ohm's Law, V = IZ where Z is a complex quantity.

Answer 5

Well I can't disagree with "MooseBoys" answer because he prefaced it with "if", but I wonder if an ohmic device can be considered "active"?
Most active devices will not obey "Ohm's law" but "MooseBoy" does state the conditions where some might.