Lorentz force is :

Options

A. the vector sum of electrostatic and magnetic force acting on a moving charged particle .
B. the vector sum of gravitational and magnetic force acting on a moving charged particle.
C. electrostatic force acting on a charged particle
D. magnetic force acting on a moving charged particle.

Answer

To solve the question regarding the Lorentz force, we need to understand its definition and the components that contribute to it.

### Step-by-Step Solution:

1. **Understanding the Lorentz Force**: The Lorentz force is the total force experienced by a charged particle moving in electric and magnetic fields. It combines the effects of both fields.

2. **Components of the Lorentz Force**:
- The force due to the electric field (\( \vec{E} \)) is given by:
\[ \vec{F}_E = q \vec{E} \]
where \( q \) is the charge of the particle.
- The force due to the magnetic field (\( \vec{B} \)) is given by:
\[ \vec{F}_B = q (\vec{v} \times \vec{B}) \]
where \( \vec{v} \) is the velocity of the charged particle and \( \times \) denotes the cross product.

3. **Combining the Forces**: The total Lorentz force (\( \vec{F} \)) acting on the charged particle is the vector sum of the electric and magnetic forces:
\[ \vec{F} = \vec{F}_E + \vec{F}_B = q \vec{E} + q (\vec{v} \times \vec{B}) \]

4. **Identifying the Correct Option**: From the options provided:
- Option 1 states that the Lorentz force is the vector sum of the electrostatic and magnetic force acting on a moving charged particle. This is consistent with our derived expression for the Lorentz force.
- Other options either mention gravitational force or only one of the forces (electrostatic or magnetic), which do not encapsulate the complete definition of the Lorentz force.

5. **Conclusion**: Therefore, the correct answer is:
\[ \text{The Lorentz force is the vector sum of electrostatic and magnetic force acting on a moving charged particle.} \]

### Final Answer:
The correct option is **Option 1**.

---