electric circuits A circuit is a closed pathway

electric circuits

• A circuit is a closed pathway

electric circuits • complete closed path through which electric charges flow

electric circuits have three parts • 1. energy source • 2. wires • 3. load

energy source examples battery photocell thermocouple electric generator

Wires • made of materials that have low resistance, like copper

loads • change electrical energy into other forms of energy, such as thermal, sound, light, or mechanical

examples of loads • light bulb • buzzer • appliances • motors

switches are important to a circuit • they close it to allow the electrons to flow through the wires • they open it to stop the flow of electrons • Video Animation: simple electrical circuit showing current flow

Most circuits have more than one load

two types of circuits • series • parallel

series circuits • a circuit in which all parts are connected in a single loop • there is only ONE path for charges to follow • all the loads share the same current

why are series circuits useful? • If there is a break in the circuit, the charges will stop flowing • Would this be helpful in your home? • EX: burglar alarms

Parallel circuits • circuit in which loads are connected side by side • the electrons have more than one path on which they can travel

why would parallel circuits be useful? Each load uses the same voltage If one load is broken or missing the electrons will still move through the other branches

circuit safety • circuits branch out from a circuit break box or “fuse box” that is the “headquarters” for that building

why might circuits fail? • broken wires or water can cause a “short circuit” • the electrons don’t go through the loads • resistance decreases, so current increases • this makes wires heat up and maybe cause a fire

fuses • thin strips of metal that electrons flow through • if the current is too high, the metal strip melts and breaks the circuit

circuit breakers • a switch that opens if the current is too high • the metal inside warms up, bends and opens the switch • circuit failure video (scroll down) • Ground fault interrupter is a small circuit breaker