does V=iR only applies resistors that obey to ohms law?

Answer 1

Its not whether the resistor obeys the ohm's law. Its about whether you're dealing with AC or DC. So with a DC input the resistor will obey the ohm law.

Answer 2

forget that stuff about 'steady state' and ac/dc. what Ohm stated was that the ratio of voltage to current is a property called resistance. every circuit must have voltage and current, so V=iR or more correctly R=V/i always applies. however for many materials, dV/di = R. Thus a "resistor" is manufactured to have this constant resistance property. Knowing in advance what the resistance should be is very helpful in calculating voltages and currents.

some commonly used devices do not display this constant resistance property, so the mathematics describing the voltage and current relationships gets complicated.

Answer 3

V=IRapplies to all condutors or resitors. for resistors that obey Ohm's law, R is constant independent of applied V, whereas for non-ohmic conductors, R depends on V.

Answer 4

Linearity is the key. Even if you have linearly-variant resistors due to temperature variations, V=IR(t) is still true However, for nonlinearly changing "resistors" such as electronic devices, the equations can get to be more complicated.

Answer 5

V= I * R applies to every situation. The equation must, however, be fully understood in order to use it.

Assumptions:
V = steady-state DC voltage
I = steady state current
R = constant resistance (or 'impedance' of which resistors, capacitors, and inductors fall) ... if it's a capacitor or inductor it gets more complicated

Deriving V=I*R is one of the first things you should learn after a Differential Equations course with an Electrical Engineering degree

A great text reference is 'Sedra and Smith'. If you want to play around with different circuits and simulate them check out 'Multsim'. http://www.ni.com/multisim