Magnetic field cannot be produced by

Options

A. changing electric field
B. moving charge
C. charge at rest
D. current-carrying wire

Answer

To solve the question "Magnetic field cannot be produced by," we need to analyze each option provided and determine whether a magnetic field can be generated by it.

### Step-by-Step Solution:

1. **Understanding Magnetic Fields**:
- A magnetic field is produced by moving charges or changing electric fields. According to Maxwell's equations, a changing electric field generates a magnetic field.

2. **Analyzing the Options**:
- **Changing Electric Field**:
- A changing electric field produces a magnetic field. This is a fundamental concept in electromagnetism.
- **Moving Charge**:
- When a charged particle (like an electron) moves, it creates a current. A current generates a magnetic field around it. Therefore, moving charges do produce magnetic fields.
- **Charge at Rest**:
- A charge that is stationary creates an electric field but does not create a magnetic field. This is because there is no movement of charge to generate a magnetic field.
- **Current Carrying Wire**:
- A wire that carries an electric current produces a magnetic field around it. This is a well-known principle in electromagnetism.

3. **Conclusion**:
- Among the options analyzed, the only scenario that does not produce a magnetic field is when there is a **Charge at Rest**.

Thus, the answer to the question "Magnetic field cannot be produced by" is **Charge at Rest**.