The intensity of a magnetic field is defined as the force experienced by a

Options

A. standard compass
B. unit positive charge
C. unit negative charge
D. unit north pole

Explanation

To solve the question regarding the definition of the intensity of a magnetic field, we will follow these steps:

### Step 1: Understand the Concept of Magnetic Field Intensity
The intensity of a magnetic field, often denoted as \( H \), is a measure of the strength of the magnetic field at a particular point in space. It is defined in terms of the force experienced by a magnetic pole placed in the field.

### Step 2: Identify the Options
The question provides four options:
1. Standard compass
2. Unit positive charge
3. Unit negative charge
4. Unit north pole

### Step 3: Analyze Each Option
- **Standard Compass**: A compass is influenced by the magnetic field, but it does not define the intensity of the field.
- **Unit Positive Charge**: This relates to electric fields, not magnetic fields.
- **Unit Negative Charge**: Similar to the positive charge, this is also related to electric fields.
- **Unit North Pole**: The intensity of a magnetic field is defined as the force experienced by a unit north pole placed in the magnetic field.

### Step 4: Conclusion
Based on the analysis, the correct definition of the intensity of a magnetic field is the force experienced by a unit north pole placed at a point in a magnetic field. Therefore, the correct answer is option 4: **Unit North Pole**.

### Final Answer
The intensity of a magnetic field is defined as the force experienced by a **unit north pole** (Option 4).

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