These days, impact printing such as that of a standard type writer has been replaced by high quality , high speed ink-jet printing . Its basic lies in building up of alphabets or figures by a jet of tiny liquid drops . Th negatively charged drops are guided by passing them between two conducing plates. A signal from a computer determines the charge on the drop. An electric field guides the drop to a particular position on the paper. About 100 tiny droplets are needed to form a single character.
Which of the following best represents the principle involved in ink-jet printing ?

Options

A. Opposite charges attract each other
B. Path of a moving charge in uniform electric field is parabola
C. When two charged drop combine, energy is released
D. Electrostatic induction.

Answer

To solve the question regarding the principle involved in ink-jet printing, we will analyze the options based on the information provided in the question.

### Step-by-Step Solution:

1. **Understanding the Process of Ink-Jet Printing**:
- Ink-jet printing involves the creation of characters or figures using tiny droplets of liquid that are negatively charged.
- These droplets are directed by an electric field created between two conducting plates.

2. **Identifying the Relevant Principles**:
- We need to identify which physical principles apply to the behavior of charged droplets in an electric field.
- The key concepts here are the behavior of charged particles in an electric field and the forces acting on them.

3. **Evaluating the Options**:
- **Option 1**: "Opposite charges attract each other."
- While this statement is true, it does not specifically describe the mechanism of directing the droplets in ink-jet printing. Thus, it is not the best representation of the principle involved.

- **Option 2**: "The path of a moving charge in a uniform electric field is a parabola."
- This statement is relevant because the negatively charged droplets will follow a curved path (parabolic trajectory) when influenced by the electric field between the conducting plates. This is indeed how the droplets are guided to specific positions on the paper to form characters.

- **Option 3**: "When two charged drops combine, energy is released."
- This option does not relate to the guiding mechanism of the droplets in the printing process, making it irrelevant.

- **Option 4**: "Electrostatic induction."
- This principle does not directly apply to the operation of ink-jet printers as described in the question.

4. **Conclusion**:
- Based on the analysis, **Option 2** is the best representation of the principle involved in ink-jet printing, as it accurately describes the path taken by the charged droplets in the electric field.

### Final Answer:
The best representation of the principle involved in ink-jet printing is **Option 2: The path of a moving charge in a uniform electric field is a parabola.**