Electric Circuits

Series and Parallel Circuits

Circuit Diagrams

• An electric circuit is a complete path through which charge can flow

• Circuit diagrams use symbols to represent parts of a circuit

• Circuit diagrams show a source of electrical energy, and devices run by electrical energy

Circuit Diagrams

• A circuit diagram will show one or more paths for the charge to flow

• Switches are where the circuit can be open • An open circuit occurs if a switch is open then

the circuit is not a complete loop and the current stops

• A closed circuit is when the switch is closed and the circuit is complete

Series Circuit

• A series circuit has only one path that the charge can flow

• If one element in a series circuit stops working then the whole circuit will not work

• Each bulb in a series circuit adds resistance and makes all of the bulbs dimmer

Parallel Circuit

• A parallel circuit is when two or more paths through which the charge can flow

• If one element stops working then the charge can flow along another path

• This is common in houses

Power and Energy

• The rate at which electrical energy is converted to another form of energy is electric power

• The unit is joule per second or watt (W)• Power is often in kilowatts (kW)• Power = current x voltage or P = I x V• P(watts) = I (amps) x V (volts)

Example

• An electric oven is connected to a 240 volt line and it uses 34 amps of current. What is the power used by the oven?

• Current = I = 34 ampsVoltage = V = 240 voltsPower = I x V

• Power = 34 amps x 240 voltsPower = 8160 watts

Electrical Safety

• There are several things needed to make a house safe such as correct wiring, fuses, circuit breakers, insulation, and grounded plugs

• In the US most houses have an average of 120 volts and each device increases the current

• If too many devices are used it may cause a fire

Home Safety

• A fuse prevents current overload in a circuit

• A wire in the fuse will melt if there is too much current

• This is how we “blow a fuse”• Most houses now use circuit

breakers• A circuit breaker is a switch that

will open when a current is too high