Immobile Particles in Electrical Engineering

In electrical engineering, there are certain particles that are considered immobile. These particles do not move when an electric current is applied. The immobile particles in electrical engineering are:

1. Ions: Ions are charged particles that can either be positively or negatively charged. They are formed when an atom gains or loses electrons. However, ions are not immobile in all cases. In some cases, they can move in an electric field, but their movement is limited.

2. Electrons: Electrons are negatively charged particles that orbit the nucleus of an atom. They are responsible for the flow of electric current in a conductor. However, in a solid material, electrons are bound to their atoms and do not move freely.

3. Holes: In a semiconductor material, the absence of an electron is called a hole. It behaves like a positively charged particle and can move in an electric field. However, in an intrinsic semiconductor, the number of holes is equal to the number of electrons, and they cancel each other's movement.

Therefore, the correct answer to the question is option 'B' - Electrons. In a solid material, electrons are immobile and do not move freely when an electric current is applied.