Question

Ohm's law is valid for

• A. Semiconductors
• B. Vacuum tubes
• C. Metal conductors
• D. Insulators

Hint:

Ohm’s law is obeyed by ohmic conductors such as metals where voltage and current are directly proportional.

Answer 1

The Correct Option is C

Concept:
Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference across it, provided the temperature and other physical conditions remain constant. Mathematically, \[ V = IR \] where:
• \(V\) = potential difference
• \(I\) = electric current
• \(R\) = resistance Ohm’s law is mainly applicable to metallic conductors because metals show a linear relationship between voltage and current under constant physical conditions.

Step 1: Understanding where Ohm’s law is applicable.
Metal conductors obey Ohm’s law because when voltage increases, current increases proportionally. Graphically, the \(V-I\) graph for metallic conductors is a straight line passing through the origin. \[ V \propto I \] Thus, metallic conductors are called ohmic conductors.

Step 2: Why the other options are incorrect.

• Semiconductors do not always obey a linear voltage-current relation.
• Vacuum tubes show non-ohmic behavior.
• Insulators practically do not allow current flow under ordinary conditions. Therefore, Ohm’s law is valid mainly for: \[ \boxed{\text{Metal conductors}} \] Hence, the correct option is: \[ \boxed{(3)\ \text{Metal conductors}} \]