1. Practical Electricity
Thirty years ago, Christmas string lights were not as popular. If one bulb burned out in the old style lights, every bulb would go out. And in order to replace the burnt out bulb, all the bulbs had to be removed and replaced until the string relit! What is the difference between old style lights and modern ones?

2. Up until this point you have been using one power source and one load for your circuits. Having a separate source for every electrical appliance or device is not very practical.
Lamps, televisions, stoves, refrigerators, computers and other devices can operate from the same source of electrical energy, yet each device can operate independently from the other (turning one on does not turn them all on!).

3. Series Circuit A series circuit has only one path for current to flow.
An advantage to a series circuit is that it is cheaper to operate.
A disadvantage to a series circuit is that if there is a break in any part of the circuit, the entire circuit is open and that means that no current can flow.
Also, the more load added to the circuit the less effective the loads become – the lights get dimmer!

4. Another disadvantage to a series circuit is that as current increases, the temperature of the conducting wires increases. If you turn on too many appliances at once, the conducting wire may get too hot and cause a fire.

6. To guard against an electrical fire, household circuits always include fuses and/or circuit breakers.
A fuse has a small metallic conductor with a melting point that is much lower that the melting point of the conducting wire. When current reaches a predetermined level (well below the amount of current needed to start a fire) the metal in the fuse melts and the current stops flowing!

7. A circuit breaker has the same function as a fuse but it accomplishes the task in a different way.
Current flows through an armature, a contact, and a bimetallic strip. If the current increases, the temperature of the bimetallic strip increases and one of the metals expands. It will bend and release a hook that will open the switch and stop the flow through the circuit.
To start the flow again, reduce the load and then simply push the armature back in place!

9. Parallel Circuit
In a parallel circuit, the different parts of the electric circuit are on separate branches, which gives electrons several options when traveling around a circuit.
An advantage to parallel circuits is that if there is a break in any part of the circuit, the electrons can find an alternate route. The current can still flow.
A disadvantage to parallel circuits is that it is much more expensive to make because of the extra material needed.