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