Physics 2009 JAMB Past Questions - Question 49: Which of the following can conduct electricity owing to the presence of free mobile electrons ?

Correct Answer

D

Explanation

Materials that can conduct electricity owing to the presence of free mobile electrons are typically classified as conductors. These materials have electrons that are loosely bound to their atoms and can move freely through the material, creating an electric current. Common examples of materials that can conduct electricity due to the presence of free mobile electrons include:

1. **Metals:** Metals like copper, aluminum, silver, and gold are excellent conductors of electricity because they have a large number of free electrons in their atomic structure.

2. **Graphite:** Graphite, which is a form of carbon, is also a good conductor of electricity because of the delocalized electrons in its hexagonal structure.

3. **Ionic solutions:** Electrolyte solutions, such as saltwater (containing dissolved ions) or acids and bases, can conduct electricity due to the movement of ions (positively and negatively charged particles) in the solution.

4. **Doped semiconductors:** When certain impurities are added to semiconductors, they become conductive. This process is called doping. Silicon, for example, can be doped to become a good conductor by introducing specific elements like phosphorus or boron.

5. **Plasmas:** In a plasma, atoms or molecules have been ionized, meaning they've lost or gained electrons, resulting in a mixture of free electrons and positive ions. Plasmas can readily conduct electricity and are often found in high-temperature environments, like stars and lightning.

Materials that do not have a significant number of free mobile electrons are known as insulators. Examples of insulators include rubber, plastic, glass, and wood. In insulators, electrons are tightly bound to atoms, making it difficult for them to move through the material and carry an electric current.