Which of the following is not an explanation for the origin of charge on the colloidal particles ?

Options

A. Due to frictional electrification
B. Due to dissociation of surface molecules
C. Due to electrophoresis
D. Due to selective adsorption of ions

Explanation

To solve the question regarding the origin of charge on colloidal particles, we need to analyze each of the given options and determine which one does not explain the origin of charge.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which of the provided options is NOT an explanation for the origin of charge on colloidal particles.

2. **Reviewing the Options**:
- **Option 1**: Due to frictional electrification.
- **Option 2**: Due to dissociation of surface molecules.
- **Option 3**: Due to electrophoresis.
- **Option 4**: Due to selective adsorption of ions.

3. **Analyzing Each Option**:
- **Option 1**: Frictional electrification can lead to the generation of charge on particles when they are rubbed against each other. This is a valid explanation for the origin of charge.
- **Option 2**: The dissociation of surface molecules can lead to the development of a charge on colloidal particles. This is also a valid explanation.
- **Option 3**: Electrophoresis refers to the movement of charged colloidal particles in an electric field. It describes the behavior of charged particles rather than explaining how they acquired their charge. Thus, this option does not explain the origin of charge.
- **Option 4**: Selective adsorption of ions on colloidal particles can lead to a net charge on these particles. This is a valid explanation for the origin of charge.

4. **Conclusion**: Based on the analysis, **Option 3 (due to electrophoresis)** is not an explanation for the origin of charge on colloidal particles. It describes the movement of charged particles rather than the mechanism by which they acquire their charge.

### Final Answer:
**Option 3: Due to electrophoresis** is not an explanation for the origin of charge on colloidal particles.