Assertion (A): Capacity of a conductor is independent on the amount of charge on it.
Reason (R ): Capacitance depends on the dielectric constant of surrounding medium, shape and size of the conductor.

Options

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is True

Explanation

To solve the question, we need to analyze both the Assertion (A) and the Reason (R) provided.

### Step 1: Understanding the Assertion (A)
The assertion states that "Capacity of a conductor is independent of the amount of charge on it."

- **Explanation**: The capacitance (C) of a conductor is defined as the amount of charge (Q) it can store per unit potential difference (V) across its plates, given by the formula:
\[ C = \frac{Q}{V} \]
This means that capacitance is a property of the conductor itself and does not change with the amount of charge stored on it. Thus, the assertion is true.

### Step 2: Understanding the Reason (R)
The reason states that "Capacitance depends on the dielectric constant of the surrounding medium, shape, and size of the conductor."

- **Explanation**: The capacitance of a conductor indeed depends on several factors:
- The dielectric constant (k) of the medium surrounding the conductor.
- The area (A) of the conductor.
- The distance (d) between the plates of a capacitor.

The formula for capacitance of a parallel plate capacitor is:
\[ C = \frac{k \epsilon_0 A}{d} \]
Here, \( \epsilon_0 \) is the permittivity of free space. The capacitance is influenced by these parameters, confirming that the reason is also true.

### Step 3: Evaluating the Relationship between A and R
Now, we need to determine if the reason correctly explains the assertion.

- The assertion is that capacitance is independent of the charge, while the reason explains that capacitance depends on the physical characteristics of the conductor and the medium. Since both statements are true and the reason provides a valid explanation for the assertion, we conclude that both A and R are true, and R is the correct explanation of A.

### Final Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct answer is:

**Both A and R are true, and R is the correct explanation of A.**