By inserting a soft iron piece into a solenoid, the strength of the magnetic field

Options

A. increases
B. decreases
C. first increases then decreases
D. remains unchanged

Explanation

### Step-by-Step Solution:

1. **Understanding the Solenoid**: A solenoid is a coil of wire that generates a magnetic field when an electric current passes through it. The magnetic field inside a solenoid is uniform and directed along the axis of the coil.

2. **Inserting a Soft Iron Core**: When a soft iron piece is inserted into the solenoid, it becomes part of the magnetic circuit. Soft iron is a ferromagnetic material, which means it can be easily magnetized.

3. **Magnetization of the Iron Core**: The magnetic field produced by the solenoid magnetizes the soft iron core. This means that the iron core will align its magnetic domains in the direction of the magnetic field created by the solenoid.

4. **Effect of Magnetization**: The magnetization of the soft iron core enhances the overall magnetic field. The iron core itself will produce its own magnetic field in addition to the magnetic field of the solenoid.

5. **Resultant Magnetic Field**: The total or resultant magnetic field inside the solenoid is the sum of the magnetic field produced by the solenoid and the magnetic field produced by the magnetized iron core. Therefore, the strength of the magnetic field increases.

6. **Conclusion**: Inserting a soft iron piece into a solenoid increases the strength of the magnetic field inside the solenoid.

### Final Answer:
The strength of the magnetic field increases when a soft iron piece is inserted into a solenoid.

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