(A) : When a Bimetalic strip made up of Brass and Iron is heated then brass lies on the convex side.
( R) : Due to lower value of coefficient of linear expansion, brass aquires convex shape.

Options

A. Both (A) and (R) are true and (R) is the correct explanation of (A)
B. Both (A) and (R) are true and (R) is not the correct explanation of (A)
C. (A) is true but (R) is false
D. Both (A) and (R) are false

Answer

To solve the question, we will analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that when a bimetallic strip made of brass and iron is heated, the brass lies on the convex side.
- This means that upon heating, the strip bends such that the brass side is on the outer curve.

2. **Understanding the Reason**:
- The reason given is that brass acquires a convex shape due to having a lower coefficient of linear expansion.
- The coefficient of linear expansion indicates how much a material expands per degree of temperature increase.

3. **Comparing Coefficients of Linear Expansion**:
- It is known that brass has a higher coefficient of linear expansion compared to iron.
- This means that when both materials are heated, brass will expand more than iron.

4. **Behavior of the Bimetallic Strip**:
- When the bimetallic strip is heated, the brass (which expands more) will push outward compared to the iron (which expands less).
- This differential expansion causes the strip to bend, with brass on the outside (convex side) and iron on the inside (concave side).

5. **Conclusion**:
- The assertion is true: brass does lie on the convex side when heated.
- The reason is false: brass does not have a lower coefficient of linear expansion; it has a higher one compared to iron.

### Final Answer:
- The assertion is true, and the reason is false.