Eddy current are produce when

Options

A. a metal is kept in varing magnetic field
B. a metal is kept in steady magnetic field
C. a circular coils is planced in a magnetic field
D. current is passed through a circular coil

Explanation

**Step-by-Step Solution:**

1. **Understanding Eddy Currents**: Eddy currents are loops of electric current that are induced within conductors by a changing magnetic field. They are called "eddy" because they flow in circular paths, similar to eddies in water.

2. **Identifying Conditions for Eddy Current Production**: Eddy currents are produced when there is a change in the magnetic field around a conductor. This can occur when a magnet moves towards or away from a metallic object or when the magnetic field itself changes.

3. **Analyzing the Given Options**:
- **Option A**: A metal is kept under varying magnetic field. This condition is correct because a varying magnetic field induces eddy currents in the metal.
- **Option B**: A metal is kept in a steady magnetic field. This condition is incorrect because a steady magnetic field does not induce any current.
- **Option C**: A circular coil is placed in a magnetic field. This condition is not necessarily true for eddy currents, as the shape of the conductor does not determine the induction of eddy currents.
- **Option D**: A current is passed through a circular coil. This condition is also incorrect for the production of eddy currents, as it does not involve a changing magnetic field.

4. **Conclusion**: The correct answer is **Option A**: Eddy currents are produced when a metal is kept in a varying magnetic field.