Electric Charges and Fields

Additivity, Conservation, Quantisation

Electric charge has three fundamental properties: (1) Additivity - charges add algebraically, (2) Conservation - total charge in an isolated system remains constant, and (3) Quantisation - charge exists in integral multiples of elementary charge e.

Metals, Human body

Conductors are materials that allow electric charges to move freely through them. Metals and the human body are good conductors because they have free electrons or ions that can move easily. Glass and plastic are insulators that resist the flow of electric charge.

Start from positive charges and end at negative charges

Electric field lines always originate from positive charges and terminate at negative charges. They never form closed loops and never cross each other. This is a fundamental property of electrostatic field lines.

Zero everywhere

According to Gauss's law, the electric field inside a uniformly charged spherical shell is zero at all points. This is because the Gaussian surface inside the shell encloses no charge, making the electric flux zero.