Which of the following graph follows Ohm's law

CONCEPT:

​Ohm's law:

• A conductor through which a current I is flowing and let V be the potential difference between the ends of the conductor. Then Ohm’s law states that

⇒ V ∝ I

⇒ V = IR

where R is called the resistance of the conductor. Resistance depends on the shape, size, and material of the conductor.

Limitations of Ohm's law:

• Ohm’s law is valid over a large class of materials.
• There do exist materials and devices used in electric circuits where the proportionality of V and I does not hold. 

The deviations in occurring are one or more of the following types:

• V is not to be proportional to I for some range of V or I

• The relation between V and I depends on the sign of V. 
  • Reversing the direction of V keeping its magnitude fixed does not produce a current of the same magnitude as I in the opposite direction.

• The relation between V and I is not unique
  • There is more than one value of V for the same current I 

EXPLANATION:

Ohm's law:

• A conductor through which a current I is flowing and let V be the potential difference between the ends of the conductor. Then Ohm’s law states that

⇒ V ∝ I

⇒ V = RI

where R is called the resistance of the conductor. Resistance depends on the shape, size, and material of the conductor.

• This equation is that of a straight line

⇒ y = mx + c

where y = V, m = R, x = I, c = 0

• Graph that is a straight line passing through origin with a positive slope follows ohms law, that is 3. T​herefore option 3 is correct. 

Important Points

• There are conditions when Ohm's law is not valid.