Define the law of conservation of electric charge and give its two examples.

Explanation

Law of conservation of charge : In an isolated system, total value of charge always remains same.
For example :
1. `""_(92)^(338) U rarr""_(90)^(334) Th + ""_(2)^(4)He`
In this decay of uranium-238, total charge before the decay (92e) and total charge after the decay (90e + 2e) remains same and hence the charge is conserved.
2. When an electron combines with a positron(annihilation of matter), the total charge before and after the annihilation remains same and hence charge is conserved.
`underset("Electron")(e^(-))+underset("Positron")(e^(+))rarrunderset("Gamma ray")(gamma+gamma)`
Charge before anihilation`=-e + e =0`
Charge after anihilation = 0
Hence, electric charge is conserved.