The SI unit of charge is the coulomb (C). It is related to the fundamental unit of charge, which is the charge of an electron or proton. The magnitude of the charge of an electron is equal to -1.602 x 10^-19 C, while the magnitude of the charge of a proton is equal to +1.602 x 10^-19 C.
This means that an electron has a negative charge and a proton has a positive charge. The charge of an object is determined by the number of electrons and protons it has. If an object has an equal number of electrons and protons, it is said to be neutral and has a charge of zero.
The charge of an object can be measured using an instrument called an electrometer. Conductors, such as metals, have a high degree of conductivity and can easily transfer charge. In contrast, insulators have a low degree of conductivity and do not easily transfer charge.
The SI unit of conductance is the siemens (S), which is the reciprocal of resistance (ohms). The conductance of a material is determined by its ability to allow the flow of electric current. The concentration of charged particles in a material can affect its conductivity. For example, increasing the concentration of ions in an electrolyte solution can increase its conductivity.