Q.Ohm's law does not apply, when (A) temperature changes
(B) temperature is constant
(C) potential difference changes
(D) none of these

Ohm's law requires physical conditions (especially temperature) to stay constant.

Ohm's law, $V = IR$ with R constant, is obeyed only when the conductor's physical state — chiefly its temperature — remains unchanged. If temperature changes, the resistivity (and hence R) changes, so the current is no longer proportional to the applied voltag …

A p-n junction diode is a non-ohmic device — its current does not vary linearly with the applied voltage.

Ohm's law states that $V \propto I$ (i.e. $V/I$ = constant = resistance) for a conductor kept at constant physical conditions. A p-n junction diode does not obey this: in forward bias, the current stays negligibly small until a threshold (knee) voltage is crossed, after which it rises very steeply and non-linearly with voltage; in reverse bias, the current stays almost constant (a small saturation current) over a …

Ohmic conductor → straight line through origin ($V\propto I$); non-ohmic conductor → curved $V$–$I$ graph.

Concept. A conductor is ohmic if it obeys Ohm's law, $V=IR$ with $R$ constant, so $V$ is directly proportional to $I$. A non-ohmic conductor (e.g. a semiconductor diode, a filament lamp, a gas discharge tube) does not obey Ohm's law — $R$ changes with the applied voltage or current.

Graph (description).

• Ohmic: a straight line passing through the origin; its constant slope $\dfrac{V}{I}=R$. …

Resistance R = tan θ when the V–I line makes angle θ with the I-axis.

Here the y-axis represents current I and the x-axis represents voltage V. The graph is a straight line making angle θ with the y-axis.

The slope of the line measured from the x-axis is (90° − θ), so …

Ohm's law (V proportional to I, i.e. a constant V/I ratio) is an empirical rule that holds for metallic conductors at constant temperature, but many important conducting devices are non-ohmic and do not obey it.

Ohm's law states that the current through a conductor is directly proportional to the potential difference across it, provided physical conditions like temperature remain constant - giving a constant resistance R = V/I.

…

Ohm's law states V = IR at constant temperature, so a V-I graph is a straight line through the origin.

Ohm's law states that for a conductor at constant physical conditions (especially constant temperature), the potential difference V across it is directly proportional to the current I flowing through it:

$V = IR$

…

Apply Ohm's law, I = V/R.

Given: V = 12 V, R = 4 kΩ = 4 × 10³ Ω.

By Ohm's law:

…

Resistance R = V/I, so its SI unit is volt per ampere, called the ohm (Ω).

Resistance is defined through Ohm's law: $R = \dfrac{V}{I}$, where V is the potential difference across a conductor (in volt) and I is the current through it (in ampere).

…

At constant temperature, V ∝ I, so V = IR.

An ohmic resistance is one whose V-I graph is a straight line through the origin; copper wire (a metal) is ohmic.

Ohm's law states that for a conductor at constant temperature, $V = IR$, i.e. the V-I graph is a straight line through the origin with slope R. Metals such as copper obey this law over a wide range of currents because their resistance depends only on temperature, not on the direction or magnitude of current.

…

By Ohm's law, $I = V/R = 4\text{ V}/2000\,\Omega = 2\text{ mA}$.

Given $V = 4\ \text{V}$, $R = 2\ \text{k}\Omega = 2000\ \Omega$.

…

By Ohm's law, $I = V/R = 2\text{ V}/1000\ \Omega = 2\ \text{mA}$.

Given $V = 2$ V and $R = 1\ \text{k}\Omega = 1000\ \Omega$. By Ohm's law, …