(A ): Coulomb force is a long range force.
(R ): Coulomb force acts along the line joining two charged particles.

Options

A. Both .A. and .R. are true and .R. is the correct explanation of .A.
B. Both .A. and .R. are tru and .R. is not the correct explanation of .A.
C. A. is true and .R. is false
D. A. is false and .R. is true

Answer

To analyze the given statements regarding Coulomb's force, we will break down the assertion and reason step by step.

### Step 1: Understand the Assertion
**Assertion (A):** Coulomb force is a long-range force.

- **Explanation:** The Coulomb force is the electrostatic force between two charged particles. It is described by Coulomb's law, which states that the force \( F \) between two point charges \( Q_1 \) and \( Q_2 \) separated by a distance \( R \) is given by:
\[ F = k \frac{Q_1 Q_2}{R^2} \]
where \( k \) is Coulomb's constant. As the distance \( R \) increases, the force \( F \) decreases with the square of the distance. However, it never becomes zero, which means that the force can act over large distances, making it a long-range force.

### Step 2: Understand the Reason
**Reason (R):** Coulomb force acts along the line joining two charged particles.

- **Explanation:** The direction of the Coulomb force is indeed along the line that connects the two charges. If the charges are of the same sign, the force is repulsive, pushing them apart. If the charges are of opposite signs, the force is attractive, pulling them together. This directional characteristic is a fundamental property of the Coulomb force.

### Step 3: Determine the Truth of Each Statement
- **Truth of A:** The assertion is true. Coulomb force is indeed a long-range force.
- **Truth of R:** The reason is also true. Coulomb force acts along the line joining the two charges.

### Step 4: Analyze the Relationship Between A and R
- **Explanation of Relationship:** While both statements are true, the reason does not explain why the Coulomb force is classified as a long-range force. The long-range nature is due to the inverse square law of the force with respect to distance, not merely because it acts along the line joining the charges.

### Conclusion
- **Final Answer:** Both A and R are true, but R is not the correct explanation of A. Therefore, the correct option is that both statements are true, but the reason does not adequately explain the assertion.