A magnetic field can exert force on a

Options

A. stationary magnet only
B. moving charge only
C. moving magnet only
D. all the above

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the conditions under which a magnetic field can exert force. We need to identify whether the force is exerted on stationary magnets, moving magnets, or charged particles.

2. **Stationary Magnets**: A stationary magnet placed in a magnetic field experiences a force. This force can be due to the interaction of the magnetic field with the magnetic field of the magnet itself.

3. **Moving Magnets**: When a magnet is in motion within a magnetic field, it also experiences a force. The motion of the magnet through the magnetic field can induce a change in the magnetic field lines, resulting in a force being exerted on the magnet.

4. **Moving Charged Particles**: According to the Lorentz force law, a charged particle moving in a magnetic field experiences a force. The force (F) on a charged particle is given by the equation:
\[ F = Q \cdot (V \times B) \]
where \(Q\) is the charge, \(V\) is the velocity vector of the charged particle, and \(B\) is the magnetic field vector.

5. **Conclusion**: Based on the above points, we can conclude that a magnetic field can exert force on:
- Stationary magnets
- Moving magnets
- Moving charged particles

6. **Final Answer**: Therefore, the correct answer is that a magnetic field can exert force on all of the above (stationary magnets, moving magnets, and moving charged particles).

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