If you want to protect a very sensitive instrument from presence of any external electric field, you will

Options

A. Put the instrument inside a wooden box
B. Put the instrument inside a copper box
C. Wrap the instrument by a plastic sheet
D. There is no way to protect it from external electric fields

Answer

To protect a very sensitive instrument from the presence of any external electric field, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electric Fields in Conductors**:
- It is known from electrostatics that the electric field inside a conductor in electrostatic equilibrium is zero. This is a fundamental property of conductors.

2. **Enclosing the Instrument**:
- To shield the sensitive instrument from external electric fields, we can enclose it within a conductor. This means placing the instrument inside a conductive material.

3. **Choosing the Right Conductor**:
- A common choice for a conductor is copper, which is widely used due to its excellent conductive properties.

4. **Placing the Instrument Inside the Conductor**:
- By placing the sensitive instrument inside a copper box (or any conductive enclosure), we ensure that any external electric field will induce charges on the surface of the conductor, thus canceling the electric field inside the enclosure.

5. **Conclusion**:
- Therefore, the sensitive instrument will be protected from any external electric field when it is enclosed in a conductive material like a copper box.

### Final Answer:
To protect a very sensitive instrument from the presence of any external electric field, you will place the instrument inside a copper box (or any conductive enclosure).

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