A: Above curie-point a ferromagnetic substance behaves as a paramagnetic substance.
R: Magnetic susceptibility of a diamagnetic substance increases with rise in temperature.

Options

A. If both Assertion & Reason are the true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reson is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To analyze the given statements about ferromagnetic and diamagnetic substances, we will break down the assertions and reasons step by step.

### Step 1: Understanding the Assertion (A)
The assertion states that "Above curie-point a ferromagnetic substance behaves as a paramagnetic substance."

- **Explanation**: The Curie point (or Curie temperature) is the temperature above which a ferromagnetic material loses its permanent magnetic properties and becomes paramagnetic. This occurs because the thermal energy at high temperatures disrupts the alignment of magnetic moments in the material, leading to a loss of ferromagnetism.

### Step 2: Evaluating the Assertion
- Since the assertion correctly describes the behavior of ferromagnetic substances above the Curie point, we conclude that **Assertion A is True**.

### Step 3: Understanding the Reason (R)
The reason states that "Magnetic susceptibility of a diamagnetic substance increases with rise in temperature."

- **Explanation**: Diamagnetic materials have a very weak and negative susceptibility to magnetic fields, which means they are repelled by magnets. However, the magnetic susceptibility of diamagnetic materials is generally considered to be nearly constant with temperature changes. In fact, it tends to decrease slightly with an increase in temperature, rather than increase.

### Step 4: Evaluating the Reason
- Since the reason incorrectly states that the magnetic susceptibility of diamagnetic substances increases with temperature, we conclude that **Reason R is False**.

### Step 5: Conclusion
- Since Assertion A is True and Reason R is False, the correct answer is that the assertion is true, but the reason is not.

### Final Answer
The correct option is: **Assertion A is True, Reason R is False**.

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