When a charge is moved against the Coulomb's force of an electric field, then

Options

A. work is done by the electric field
B. energy of the system is decreased
C. strength of the field is decreased
D. energy is used from some outside source

Answer

To solve the question "When a charge is moved against the Coulomb's force of an electric field, then...", we need to analyze the situation step by step.

### Step-by-Step Solution:

1. **Understanding Coulomb's Force**:
- When a charge (let's say a positive charge) is placed in an electric field, it experiences a force due to that field. The direction of this force is the same as the direction of the electric field lines.

2. **Movement Against the Electric Field**:
- If the charge is moved against the direction of the electric field, it means that we are applying an external force to move the charge in the opposite direction to the force exerted by the electric field.

3. **Work Done**:
- Work is defined as the product of force and displacement in the direction of the force. When moving against the electric field, work is done on the charge by an external agent (not by the electric field).
- Mathematically, if \( F \) is the force exerted by the electric field and \( d \) is the displacement in the opposite direction, the work done \( W \) is given by:
\[ W = F \cdot d \]
- Since the displacement is against the electric force, the work done is positive.

4. **Energy Considerations**:
- As the charge is moved against the electric field, energy is required. This energy is supplied by an external source (like a battery or another force). Therefore, the energy of the system increases because work is done on the charge.

5. **Conclusion**:
- The correct statement regarding the movement of a charge against the Coulomb's force of an electric field is that energy is used from some outside source to move the charge against the electric field.

### Final Answer:
When a charge is moved against the Coulomb's force of an electric field, energy is used from some outside source.

---