(A): Magnetic field lines can be entirely confined within the core of a toroid. But not within a straight solenoid.
(R) : The magnetic field inside the solenoid is uniform.

Options

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

Answer

To solve the problem, we need to analyze the two statements given in the question:

**Statement (A):** Magnetic field lines can be entirely confined within the core of a toroid but not within a straight solenoid.

**Statement (R):** The magnetic field inside the solenoid is uniform.

### Step-by-Step Solution:

1. **Understanding the Toroid:**
- A toroid is a doughnut-shaped coil of wire. When current flows through the wire, the magnetic field lines are generated inside the toroid.
- The magnetic field lines are circular and confined within the core of the toroid. There are no open ends, which means that the magnetic field does not extend outside the toroid.

2. **Understanding the Solenoid:**
- A solenoid is a long coil of wire. When current flows through the solenoid, it generates a magnetic field.
- Inside the solenoid, the magnetic field is uniform and parallel to the axis of the solenoid. However, the ends of the solenoid are open, allowing magnetic field lines to extend outside of it.

3. **Analyzing Statement (A):**
- The first statement claims that magnetic field lines can be entirely confined within the core of a toroid but not within a straight solenoid. This is true because:
- In a toroid, the magnetic field is completely contained within its structure.
- In a solenoid, the magnetic field lines extend outside the solenoid, especially at the ends.

4. **Analyzing Statement (R):**
- The second statement claims that the magnetic field inside the solenoid is uniform. This is also true because:
- The magnetic field inside a long solenoid is uniform and parallel, meaning it has the same strength and direction at all points inside the solenoid.

5. **Conclusion on the Relationship:**
- While both statements are true, statement (R) does not explain why statement (A) is true. The confinement of magnetic field lines in a toroid is due to its closed-loop structure, while the uniformity of the magnetic field in a solenoid is a separate characteristic.
- Therefore, the correct option is that both statements are true, but (R) is not the correct explanation for (A).

### Final Answer:
Both statements (A) and (R) are true, but (R) is not the correct explanation for (A).

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