household electricity.ppt

7/27/2019 household electricity.ppt

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Chapter 5

Using Electricity in the Home


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Work = force (Newtons) X distance (m)

In order to do work a force must movethrough a distance.

Kinetic energy involves movement or use Potential energy means that it can be used

On Earth we can convert our weight in

kilograms to Newtons by multiplying by 10i.e.. One kilogram becomes 10 N


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Energy = Voltage X Current X

time The units for energy are joules (J)

Power = energy / time

Power = Voltage (v) X Current (I)


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House Hold Energy

Consumption Hydro bills are established by finding

out how many kilowatt hours of

electricity your household has used in agiven time.

1 kWh = kilowatts X time (hours)

1 kWh = 1 000 Watts X 1 hour

1 kWh = 1 000 W X 3 600 seconds


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Reading the Meter always

use the smallest number


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This reading should be 88762


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Efficiency This is a comparison of the amount of

energy obtained as compared to the

amount of energy put into the system

Efficiency = energy output / energy input

To convert it to a percentage just multiplythe answer by 100 %


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House Hold Wiring The wires coming into a house include a black, a

red and a white.

The blackand the redwires are hot

The white wire is neutral leading to a ground

The black is rated as being 120 v from the neutral The red is rated as being 120 v from the neutral


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Electricity Entering Your House

Red = In at 120V

Black = Out at 120VPotential difference = 240V


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Household Wiring is in ParallelWhich connecting wire, A, B, C,

D, or E, will be the first to

become dangerously hot if toomany appliances are turned on?

How can overheating be prevented,

even if all the appliances in the

house are turned on


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Alternating Current Frequency In North America, the current alternates back

and forth in what we call cycles per second

1 cycle/second = 1 Hertz

Electrical frequency in North America = 60 Hz


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The Service Panel Since the service panel has black, red, and

white wires, the total voltage is 120 + 120 =240 volts.

The service panel usually contains circuitbreakers. The breakers have either a red ora black wire attached to them.

The service panel provides electricity for thebranch circuits.


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Usually 15 ampbreaker

30 amps or greater


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Powerful Devices


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The Neutral Wire (White) The neutral wire is the ground

Grounds protect us from electrocution

Service Panel has a ground wire

3 prong plug the circular, bottom holeleads to the ground buried outside.


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The Neutral Wire (White) The neutral wire is _____________

Grounds protect us from __________ Service Panel has a ______________

3 prong plug the circular, bottom hole

_________________________________.


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Three Prong Plug


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Circuit Breakers Circuit breakers open the circuit when a

current in a house wire exceeds the ratedcurrent for that circuit.

The circuit breaker protects people frombeing electrocuted to death and protects usfrom burning down the house.

Circuit overloads cause the generation ofheat.


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Circuit breakers - Details Ordinary breakers are rated as 15 amps.

There are bigger breakers provided for suchcircuits that require 240 volts e.g.. Dryersand water heaters.

Instead of circuit breakers some electricaldevices have fuses. Often electric stoveshave fuses.


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Fuses are Older than Circuit of

Breakers

When ribbon carries too much current,

it melts, interrupting the current.


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GFCI Ground Fault Circuit

Interrupter1. Detects current

differences in the neutraland hot wire

2. Should be same

3. If not, the internalbreaker goes immediately

4. Can reset

5. Use near water sourceswhere safety is concern

6. Bathroom, outdoor outlets
http://thebarn.virtualave.net/ex/electrical/gfci.jpg


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House Hold Wiring

House hold circuits are 120 volts and are alternatingcurrent. Appliances are usually connected in parallel.

The circuits are polarized. That is, the black wire isconnected in a certain way and the neutral wire isconnected in a certain way.

Polarized plugs reduce the risk of an electrical shockby forcing electricity to flow in one general direction


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Types of PlugsUsed in the

Home

Drier Plug orStove Plug

(Ground)

Lamp Plug orHair Dryer

(Polarized)


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Three Prong Plug


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Three pronged plug The round prong is the ground

The longer hole is connected to the white

wire (neutral). We need this wire tocomplete the circuit.

The shorter hole is connected to the black

wire.(hot120 Volts)

The grounded plug is safer than a twopronged plug.


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Grounding the Current The service panel is connected to a long

metal stake that buried outside the house.

If a person is electrocuted most of thecurrent will go to ground.

In much older houses the wiring isgrounded on the copper water pipes.


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Ground Wire


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Improperly Grounded Appliance with Short

One milliampere: tingling sensationTen milliamperes: nerves and muscles overloaded200 milliamperes: potentially fatal; heart fibrillation500 -1000 milliamperes: not necessarily fatal; heart willrestart -- One ampere or more: burn alive


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Grounded Appliance


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Ground Plugs Prevent You frombecoming the Shortest, Easiest Path to

the Ground!!


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Avoid! Or.. Thou Shalt Not!

1. Frayed electrical wires

2. Octopus outlets

3. Water and electrical wires

4. Plug receptacles to protect smallchildren

5. Over loading electrical circuits

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