The susceptibility of a perfectly diamagnetic substance is

Options

A. 0
B. 1
C. `-1`
D. Less than 1

Answer

To find the susceptibility of a perfectly diamagnetic substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Susceptibility**:
- Susceptibility (χ) is a measure of how much a material will become magnetized in an applied magnetic field.

2. **Know the Relative Permeability of Diamagnetic Substances**:
- For diamagnetic materials, the relative permeability (μ_r) is less than 1. In the case of a perfectly diamagnetic substance, we can consider μ_r to be equal to 0.

3. **Use the Relationship between Relative Permeability and Susceptibility**:
- The relationship between relative permeability and susceptibility is given by the formula:
\[ \mu_r = 1 + \chi \]
- Here, χ is the susceptibility.

4. **Substitute the Value of μ_r for Perfectly Diamagnetic Substance**:
- Since we are considering a perfectly diamagnetic substance, we can set μ_r = 0.
- Substitute this value into the equation:
\[ 0 = 1 + \chi \]

5. **Solve for Susceptibility (χ)**:
- Rearranging the equation gives:
\[ \chi = 0 - 1 = -1 \]

6. **Conclusion**:
- Therefore, the susceptibility of a perfectly diamagnetic substance is:
\[ \chi = -1 \]

### Final Answer:
The susceptibility of a perfectly diamagnetic substance is **-1**.

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