A :Alloys of metals usually have greater resistivity than that of their constituent metals.
R : Alloys usually have much lower thermal coefficient of resistance than pure metals.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion , then mark
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion then mark.
C. If Assertion is ture statement but Reason is false , then mark
D. If both Assertion and Reason are false statements then mark.

Answer

To analyze the given statements regarding alloys and their properties, we will break down the assertions and reasons step by step.

### Step 1: Understanding Assertion (A)
**Assertion (A): Alloys of metals usually have greater resistivity than that of their constituent metals.**

- **Explanation**: This statement is true. When metals are combined to form alloys, the arrangement of atoms is disturbed due to the presence of different atomic radii and electronegativities of the constituent metals. This disturbance leads to increased resistivity because the conduction of electrons is hindered.

### Step 2: Understanding Reason (R)
**Reason (R): Alloys usually have a much lower thermal coefficient of resistance than pure metals.**

- **Explanation**: This statement is also true. The thermal coefficient of resistance indicates how much the resistance of a material changes with temperature. Alloys are often designed to have stable electrical properties over a range of temperatures, which results in a lower thermal coefficient of resistance compared to pure metals.

### Step 3: Analyzing the Relationship Between A and R
- While both statements A and R are correct, we need to determine if R correctly explains A.
- The assertion discusses the resistivity of alloys, while the reason discusses the thermal coefficient of resistance. Although they both relate to electrical properties, the reason does not directly explain why alloys have greater resistivity.

### Conclusion
- Both the assertion and the reason are correct, but the reason does not adequately explain the assertion. Therefore, the correct answer is that both statements are true, but R does not explain A.

### Final Answer
- Both A and R are correct, but R is not the correct explanation for A.

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