Unit 2: ElectricityLesson 8: Household Electricity
By the end of the lesson you should be able to: Explain the difference between AC and DC Describe the difference between breakers and
fuses Label the wires in plugs and outlets Read electrical meters and Energuide labels Describe how 3-way switches work
Direct Current (DC): Electrons flow from
negative to positive only
Produced by dry cells
Alternating Current (AC):
Electrons flow one way and then the polarity reverses
Used in houses and industry
Switches 60 times per second (60 Hz)
Breakers: Made of bi-metallic
strip that bend at different temps and causes the circuit to break
Found in thermostats, breaker panels
Can be reset and reused – but only after the problem is fixed!
Fuses: A wire inside a case
that will melt with too much current
Found in stoves, cars, radios
Cannot be reset, must be replaced
Typically 15 A or 20 A
3 wires enter your house:1. One 120 V wire2. Another 120 V wire3. A ground wire
1 and 2 are called “hot wires” The ground is neutral All 3 wires must pass through the
electrical meter on the outside of your house
All circuits are in parallel…why?
Large prong = neutral, returns electrons
Smaller prong = hot, source of electrons
Round bottom = ground, connects to ground rod
Occur when one side of the plug/outlet is smaller/wider than the other
Used so the switch can be on the hot wire so when its off there no voltage difference between the terminals so there is less chance of electrocution
A path of little resistance so current will increase and trip the breaker
Connects an appliance to the ground via the appliance case
Used to measure energy used in your home
The more energy you use the faster the dials turn
The dials are interlocking so they spin in opposite directions
When an arrow is between two numbers always choose the lower one
Practice reading meters on the worksheet
1. Energy consumed per year
2. This model as it compares to other makes and models in this class
3. Range of energy usage of other makes and models in this class
4. Types and range of similar models
We add resistors to household circuits by plugging them in!
Resistors slow electrons down so there is less heat
Less heat = less chance of a fire!
Normal voltage is 120 VHeavy duty voltage is 240 V
Used in staircases so we can control the lights at the top and bottom of the stairs