Do all electrical and electronic circuits obeys ohms law?

Answer 1

Ohm's law is always true. That's what makes it a law. What trips people up is that resistance is not constant. The law states that voltage is current times resistance. That is true, no matter what. The calculations can become complex, because resistance is not constant.

Another AnswerProbably not. But it really depends on the shape of the characteristic curve for its application (e.g. diode).

Despite being fundamental, Ohm's Law is one of the least understood so-called 'laws' in electrical engineering. It applies in so few cases, in fact, that many engineers and physicists argue that it should not be called a 'law' at all!

Ohm's Law is not a universal law, and onlyapplies when the ratio of voltage to current is constant for variations in voltage. This only applies to linear or 'ohmic' devices. Most electronic devices are non-linear or 'non-ohmic' and these include vacuum tubes and solid-state devices, etc. Even some pure metals, such as tungsten, are non-linear -so incandescent lamps, for example, do not obey Ohm's Law.

Ohm's Law only applies to conductors and circuit devices that produce a straight-line graph when current is plotted against variations in voltage. If the resulting graph is curved, then Ohm's Law doesn't apply. Period!

Think about it: if you, say, double the voltage for a curved graph line, the resulting current doesn't double in value -so it can't be obeying Ohm's Law (which states that 'current is proportional to voltage').

Of course, some vacuum tubes and solid-state devices have voltage/current characteristic curves that are partly-curved and partly-straight -in these cases Ohm's Law applies only the the straight-line parts of those characteristic curves, but not to the curved parts. Some devices have 'negative' curves, in which current increases when the applied voltage decreases -clearly these do not obey Ohm's Law, either!

Having said that, for non-linear devices, you can use the ratio of voltage to current (= resistance) to find out what the resistance happens to be for any particular ratio of voltage to current -i.e. at a specific point along their graph line.

Answer 2

Ohm's law only applies to resistive circuits with a single power source.