Conservation of Charge — Definition
Definition
Imagine you have a closed box, and inside this box, there are some positive and negative electric charges. The principle of conservation of charge simply says that no matter what happens inside that box – whether the charges move around, interact, or even if new particles are created or old ones disappear – the *total* amount of electric charge inside the box will always stay the same.
You can't magically create new charge out of nothing, nor can you make existing charge vanish into thin air. You can only move it around or change its form, but the net sum remains constant.
Think of it like money in a closed economy. If you have a certain amount of money circulating, it might change hands, people might earn it or spend it, but the total amount of money in that economy doesn't just appear or disappear. It's conserved. Similarly, electric charge is a fundamental property of matter, and its total quantity is conserved.
For example, if you rub a glass rod with a silk cloth, the glass rod becomes positively charged and the silk cloth becomes negatively charged. Before rubbing, both were electrically neutral, meaning their total charge was zero.
After rubbing, the glass rod gains a certain amount of positive charge, say , and the silk cloth gains an equal amount of negative charge, . If you add these charges together (), the total charge is still zero.
What happened? Electrons (which carry negative charge) were transferred from the glass rod to the silk cloth. No new charge was created; it was merely redistributed.
This principle is incredibly powerful because it applies to everything, from simple everyday phenomena to complex nuclear reactions. It's a fundamental law of nature, meaning it's always observed to be true, without exception, in any isolated system. An 'isolated system' here means a system where no charge can enter or leave from its boundaries. This ensures that any change in charge within the system is due to internal processes, not external influences.