Which of the following statements is not ture ?

Options

A. Paramagnetic substances are weakly attracted by a magnetic field.
B. Ferromagnetic substances cannot be magnetised permanently .
C. The domains in antiferromagnetic substance are oppositely oriented with respect to each other.
D. Pairing of electrons cancels their magnetic moments in the diamagnetic substances.

Answer

To determine which of the following statements is not true, we will analyze each option one by one:

1. **Option 1: Paramagnetic substances are weakly attracted by a magnetic field.**
- **Analysis:** This statement is true. Paramagnetic substances have unpaired electrons, which allow them to be weakly attracted to a magnetic field.

2. **Option 2: Ferromagnetic substances cannot be magnetized permanently.**
- **Analysis:** This statement is false. Ferromagnetic substances can be magnetized permanently due to their strong magnetic properties and the alignment of their magnetic domains. Therefore, this statement is incorrect.

3. **Option 3: The domains in antiferromagnetic substances are oppositely oriented with respect to each other.**
- **Analysis:** This statement is true. In antiferromagnetic materials, the magnetic moments of adjacent atoms or ions are aligned in opposite directions, resulting in no net magnetization.

4. **Option 4: The pairing of electrons cancels their magnetic moments in diamagnetic substances.**
- **Analysis:** This statement is true. In diamagnetic substances, all electrons are paired, and their magnetic moments cancel each other out, resulting in a weak repulsion from a magnetic field.

**Conclusion:** The statement that is not true is **Option 2: Ferromagnetic substances cannot be magnetized permanently.**