Assertion : V = iR is Ohm's law.
Reason : V - I graph is always a straight line passing through origin.

Options

A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are true and Reason is not correct explanation of Assertion.
C. If Assertion is true but Reason is false.
D. If Assertion is false but Reason is true.

Answer

To solve the assertion and reason question, we need to analyze both statements carefully.

### Step 1: Understand the Assertion
The assertion states that "V = iR is Ohm's law."
- **Explanation**: Ohm's law indeed states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, provided the temperature and physical state of the conductor remain constant. The equation V = iR represents this relationship, where R is the constant resistance.

### Step 2: Understand the Reason
The reason states that "V - I graph is always a straight line passing through the origin."
- **Explanation**: The V-I graph (Voltage vs. Current graph) is a straight line passing through the origin only for ohmic conductors, where the resistance remains constant. However, for non-ohmic conductors, the graph can be non-linear, meaning it does not always pass through the origin or remain a straight line.

### Step 3: Analyze the Relationship Between Assertion and Reason
- The assertion is true because V = iR is indeed Ohm's law.
- The reason is false because the V-I graph does not always represent a straight line passing through the origin for all types of conductors. It is only true for ohmic conductors.

### Conclusion
- **Assertion**: True
- **Reason**: False
- Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer
The assertion is true, and the reason is false. The correct option is C.

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