The strength of magnetic field due to a solenoid depends on the

Options

A. current through it
B. material of core
C. number of turns
D. all of these

Explanation

To determine the factors on which the strength of the magnetic field due to a solenoid depends, we can analyze the formula for the magnetic field inside a solenoid.

### Step-by-Step Solution:

1. **Understanding the Formula**:
The magnetic field \( B \) inside a solenoid can be expressed using the formula:
\[ B = \mu_0 \cdot n \cdot I \]
where:
- \( B \) is the magnetic field strength,
- \( \mu_0 \) is the permeability of free space (a constant),
- \( n \) is the number of turns per unit length of the solenoid,
- \( I \) is the current flowing through the solenoid.

2. **Identifying the Variables**:
- The strength of the magnetic field \( B \) depends on:
- The **current** \( I \): As the current increases, the magnetic field strength increases.
- The **number of turns per unit length** \( n \): More turns per unit length result in a stronger magnetic field.
- The **permeability of the material** inside the solenoid: If the solenoid has a core material, the relative permeability \( \mu_r \) of that material will also affect the magnetic field strength. The modified formula becomes:
\[ B = \mu_0 \cdot \mu_r \cdot n \cdot I \]

3. **Conclusion**:
From the analysis, we conclude that the strength of the magnetic field due to a solenoid depends on:
- The current \( I \),
- The number of turns per unit length \( n \),
- The permeability of the core material \( \mu_r \).

### Final Answer:
The strength of the magnetic field due to a solenoid depends on the current \( I \), the number of turns per unit length \( n \), and the relative permeability \( \mu_r \) of the core material.

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