Circuit breakers are the single most important piece of safety equipment in your home. They are vital in protecting you and your appliances from surges in electricity that can cause electrical fires and destroy electrical appliances. Whenever the circuit senses too much power it cuts the circuit before any damage is done. This allows you or an electrician to troubleshoot the problem.
Before working on any live outlets its advisable to cut that breaker or even cut the main power circuit if you aren’t sure exactly which circuit the outlet is on.
>How Circuit Breakers Work [How Stuff Works]