Charge

Charge is a fundamental property of an object, and defines how electrical objects attract or repel each other. It is used to determine the electric force on objects.

Charge

$$1\text{C}=1\text{As}=q_e^{-1}=\text{Charge of }\sim 6.24\times 10^{18}\text{ electrons}$$

• Fundamental property for:#physics/electromagnetism/electric phenomena
• Defined with the fundamental constant: $q_e$, the elementary charge, which is defined as the charge of an electron or proton. First discovered from Oil Drop Experiment
• SI Base Units: $\text{As}$ (Ampere-second)
• Algebraic Symbol: $q$ (Sometimes $Q$)

Derivations of Charge (Time-independant)

$$q=\frac{\Delta U}{\Delta V}=\frac{kq}{r^2}=\frac{1}{{ϵ}_0}{\Phi }_E$$

1. Electric Potential
2. Electric Field
3. Gauss’ Law

Derivations of Charge (Time-dependant)

$$q={\int }_{t_i}^{t_f}I(t)\text{d}t$$

Note

• $q$ = Charge flowed through a single point (in $\text{C}$)
• $I$ = Current (in $\text{A}$)
• $t$ = Time period (in $s$)

Charge Carriers §

In a hypothetical mathematical mode, how the charge moves is not as important, just the rate. But in the real world, our movement of charge is heavily dependant on the charge carriers, which are particles that hold some charge, and ‘carry’ it along paths.

Charge Conductivity is also a result of the nature of the charge carriers, which depend on the chemical structure of the material. Here’s a simple table to remember them:

Material	Charge Carrier
Metals	Free-moving valence electrons
Non-metals*	Tightly held-in-place electrons
Electrolytes#todo	Ions (Cations & Anions)
Plasma	Electrons and Cations (+Ions)
Semiconductors	Electrons and holes

*Certain non-metals such as graphite behave like metals in terms of conductivity Holes are absences of electrons