Assertion (A): Alloys are commonly used in electrical heating devices like electric iron and heater.
Reason (R): Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points then their constituent metals.

Options

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

Answer

To solve the question, we need to analyze both the Assertion (A) and the Reason (R) given in the statement.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Alloys are commonly used in electrical heating devices like electric iron and heater."
- This statement is true. Alloys, such as nichrome (which is made of nickel and chromium), are indeed used in heating elements due to their properties.

2. **Understanding the Reason (R)**:
- The reason states that "Resistivity of an alloy is generally higher than that of its constituent metals but the alloys have low melting points than their constituent metals."
- The first part of this statement is true: alloys typically have higher resistivity than their pure constituent metals, which is beneficial for heating applications as it allows for more heat generation.
- However, the second part of the reason is false: alloys generally have higher melting points than their constituent metals. This is crucial because for heating elements, we need materials that can withstand high temperatures without melting.

3. **Conclusion**:
- Since the assertion is true and the reason is false, we conclude that the correct relationship is that the assertion is true but the reason is false.

### Final Answer:
- The correct option is: **Assertion is true, but reason is false.**