The development of electrical charge when different materials are rubbed together can be attributed to the phenomenon called triboelectricity. Triboelectricity is a branch of contact electrification that deals with the generation of electric charges on the surfaces of materials during contact and separation. Here's why objects made from different materials develop an electrical charge when rubbed:

1. Charge Separation: When two different materials come into contact, there is an exchange of electrons between them. This exchange occurs because of differences in their work functions. The work function is the minimum energy required to remove an electron from the surface of a material. Materials with a lower work function tend to donate electrons more easily, while materials with a higher work function tend to accept electrons.

2. Electron Transfer: When the two materials are brought into contact, the electrons from the material with the lower work function will flow to the material with the higher work function. This creates an excess of electrons on one surface and a deficiency of electrons (positive charge) on the other. As a result, one object becomes negatively charged, and the other becomes positively charged.

3. Separation of Charges: When the two materials are separated after being in contact, the charges created on their surfaces remain separated. This is because the electrostatic force between the positive and negative charges holds them in place. The magnitude of the charge depends on various factors, including the nature of the materials, the surface roughness, the contact area, and the separation distance.

It's worth noting that the charging behavior of materials is complex, and the exact mechanisms can vary depending on the specific materials involved. However, the general principles of charge separation and transfer described above apply to most cases of triboelectricity.