The width of the forbidden band will be small in

Options

A. metals
B. insulators
C. semiconductors
D. good conductors

Answer

To determine the material in which the width of the forbidden band (energy gap) is small, we can analyze the characteristics of metals, insulators, semiconductors, and good conductors.

### Step-by-Step Solution:

1. **Understanding Forbidden Band**: The forbidden band, or energy gap, is the energy difference between the valence band (the highest range of electron energies in which electrons are normally present) and the conduction band (the range of electron energies higher than the valence band, where electrons can move freely and conduct electricity).

2. **Characteristics of Metals**: In metals, the conduction band and valence band overlap. This means that there is no forbidden band, or the width of the forbidden band is effectively zero. Therefore, metals are excellent conductors of electricity.

3. **Characteristics of Insulators**: Insulators have a large forbidden band. The energy gap between the valence band and the conduction band is significant, which prevents electrons from moving freely and conducting electricity. This results in poor conductivity.

4. **Characteristics of Semiconductors**: Semiconductors have a small forbidden band. The energy gap between the valence band and the conduction band is small compared to insulators. This allows some electrons to jump from the valence band to the conduction band under certain conditions (like temperature increase or doping), enabling them to conduct electricity, but not as effectively as metals.

5. **Conclusion**: Since we are looking for the material with a small width of the forbidden band, we find that semiconductors have a small forbidden band compared to insulators and metals. Therefore, the correct answer is semiconductors.

### Final Answer:
The width of the forbidden band will be small in **semiconductors**.