Circuit Breaker Types
Standard Circuit breakers detect an electrical overload and instantly turn off to avoid danger.
Ground Fault Interrupt breakers detect overload, but addtionally detect problems (surge) in grounding.
15 amp breakers are typical in residential use for outlets and lighting. Each circuit groups electrical service to an individual room. Sometimes a room will require multiple 15 amp breakers.
For wet locations such as bathrooms, kitchens, garage, or outside, a Ground Fault Interrupt (GFI) circuit breaker is used unless GFI protection is provided at the location of the outlets or lights.
Circuit and Breaker Loading
A 15 amp breaker can deliver current for a maximum of 1800 watts. An example of a fully loaded 15 amp circuit would be 18 light bulbs each rated at 100watts. If you switched on a 19th lamp, the circuit breaker will "trip" to the OFF position and current to the circuit will go off. (Electrical devices like light bulbs can vary so it's actually possible to draw slightly more than 1800 watts with the 18th bulb and have the breaker trip sooner).
18 100-Watt Light Bulbs
Maximum load for a 15 amp circuit
It's a little harder to imagine the load when a television, lamps, and a fan are all plugged into the same circuit but generally a 15 amp circuit can carry the load reasonable for a room. However, a heavy duty applicance such as window air conditioner or heater could cause an overload on a 15 amp circuit. Window air conditioners come in various sizes. Most smaller units will run on a 15 amp circuit but you may not be able to run much else with it.
Larger window air condtioners, will typically require a 20amp circuit. Check the unit specifications before you buy.
Larger electrical applicances like stoves and clothes dryers require significantly more energy.
Special "Side-by-Side" Circuit Breakers are in the Circuit Breaker box that provide 40, 50 or more amps, at a higher voltage (220V) and these required heavier wire to carry the load too.