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Home Electric Wiring Home Electric Wiring

Home Electric Wiring - PowerPoint Presentation

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Uploaded On 2017-09-14

Home Electric Wiring - PPT Presentation

SNC1P Home Electric Wiring Most Homes in Ontario are connected to a Power Transmission Grid The grid is a huge circuit It covers hundreds of kilometres The grid connects each building to a power source The power station is the source of electric energy ID: 587822

current circuit electric fuse circuit current fuse electric appliances draw breaker device overloaded devices parallel 120 carry connected designed

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Slide1

Home Electric Wiring

SNC1PSlide2

Home Electric Wiring

Most Homes in Ontario are connected to a

Power Transmission Grid

. The grid is a huge circuit. It covers hundreds of kilometres. The grid connects each building to a power source. The power station is the source of electric energy. Slide3

Electric wires carry current to each building through a

central electric panel

. A number of separate circuits carry current from the central electric panel to different parts of the home. The arrangement of circuits in a building is often called the

wiring. Slide4

Each circuit in the house is designed to handle a certain number of loads safely. Special circuits may also be designed for certain kinds of loads. Only qualified electricians should ever try to change wiring in a home. Slide5

Question:

Think about the series and parallel circuits you have built

What will happen in your home if you connect too many electrical devices in parallel in the same circuit?

The circuit breaker will cut off power to avoid the chance of a fire. Slide6

Know your voltage

In North America, most household electric circuits carry 120 V. However, different electrical devices operate at different voltages

120 V

A regular household electric current is connected to a 120 V circuit

Some household outlets are connected to a 240V circuit. Slide7

It is very important to make sure each device is plugged in at its correct voltage. If the voltage is too low, the device will

not work

. If the voltage is too high, the device will be

damaged. The circuit inside the device may even explode. This can hurt people or start a fire. Slide8

Some Large appliances work at 240 V. Electric stoves, freezers, and clothes dryers are examples of appliances that may need 240 V. These appliances have special outlets. A regular electric plug will not fit into a 240 V outlet. Slide9

Many devices operate at less than 120 V. A device that operates at 12 V cannot be plugged directly into a regular 120 V outlet. Instead, the plug carries current through a

transformer

.

The transformer reduces the voltage to 12 V. Slide10

Question

When will an electric device require a transformer?

When the voltage is too high

Why are 240 V outlets shaped differently from 120 V outlets?To prevent 120 v appliances from being damaged Slide11

Know Your Current

Every electrical device needs a certain amount of electric current. Different kinds of devices use, or

draw

, different amounts of current. Appliances that convert electricity to heat usually draw more current than other kinds of appliances. Slide12

Remember, when loads are added in parallel, the total current in the circuit increases. The same thing happens when you connect more devices to an electric circuit by adding up the current draw by each device. Slide13

Example: An electric kettle draws about 8 A. A clock radio draws about 1 A. If you connect both of these appliances in one parallel circuit, the total current in the circuit is 8 A + 1 A = 9 A.

Kettle 8 A

Clock radio 1 ASlide14

An electrician planning a home electric system must think about what kinds of appliances will be used in the home. The electrician must also think about where these appliances will be used. Each circuit must be designed to carry the right amount of current for its intended use. Slide15

What is the total current in this circuit?

3A + 3A + 3A + 3A = 12 A

3A

3A

3A

3ASlide16

Draw a circuit for each situation.

Draw an A.C. power source with one 3A bulb in parallel with one 6 A bulb.

 

What is the total current draw in the circuit?Slide17

Draw a circuit for each situation.

Draw an A.C. power source with one 3A bulb in parallel with one 4A bulb and one 5A bulb.

 

What is the total current draw in the circuit?Slide18

Fuses and Circuit BreakersSlide19

Fuses and Circuit Breakers

Each circuit in a home is designed to carry a certain maximum current. A 15 A circuit can carry up to a maximum of 15A of current. If the current is less than 15 A, the circuit is safe.

IF the current rises

above 15 A, the circuit is overloaded. Slide20

A circuit can become overloaded when too many devices are connected in parallel. A

short circuit

can also cause a circuit to overload. Slide21

An overloaded circuit can be dangerous. The conducting wires can heat up and start a fire. To make sure this does not happen, each circuit in a home is protected by either a

fuse

or a circuit breaker. Fuses and circuit breakers are important electric safety devices. They are designed to stop current from flowing in an overloaded circuit until the problem is fixed. Slide22

For the following two examples, write “safe” if the circuit is safe. Write “overloaded” if the circuit is overloaded. Show how you know. Slide23

A)

Safe

3 + 3 + 2 + 2 = 10 A

2 A

2 A

3 A

3 ASlide24

B) 15 A

overloaded

2 + 3 + 3 + 3 + 6 = 17

2 A

3 A

3 A

3 A

6 ASlide25

How a Fuse Works

What is the circuit symbol for a fuse?Slide26

A fuse prevents too much current from flowing through a circuit. If the current is too high, the wire conductor inside the fuse melts. This opens the circuit. No electrical device on the circuit will work until the fuse has been replaced. Slide27

15 ASlide28

An intact fuse. Current flows through the wire inside the fuse. The circuit is

closed.Slide29

A “

blown

” fuse. The wire has melted. Current does note flow through the wire. The circuit is

open. Slide30

Many homes have a

fuse box

. The fuse box holds all the fuses for all the circuits in the house or apartment.

The fuse box is connected to the central electric panel. Slide31

If you are replacing a fuse, always make sure that new fuse is exactly the right kind. If a new fuse blows right away, do not replace it again. Have an electrician check the circuit. There may be a problem in the electric system. Slide32

Why could it be dangerous to put the wrong kind of fuse in a circuit?

It could allow too much current through which could damage things or lead to a fire. Slide33

Fuse boxes are not just in homes. Cars, trucks, motorcycles, stereo equipment and various other devices all have fuse boxes in them to protect their electrical equipment. Slide34

An electric circuit connects three bulbs in parallel. Each bulb draws 3 A. One 10 A fuse protects the circuit.

Draw a diagram of the circuit

Explain what happens when a space heater that draws 12 A is connected to the circuit. Slide35

The fuse will blow

10 A

3A

3A

3A

12 ASlide36

How a circuit breaker works

A circuit breaker is designed to cut off electric current in an overloaded circuit just like a fuse does. A circuit breaker works like switch. If the circuit is overloaded, the circuit breaker

trips

. This opens the circuit. After the problem has been fixed, the circuit breaker can be reset to close the circuit. Slide37

What is the symbol of a circuit breaker? Slide38

One advantage of a circuit breaker is that it can be used over and over again. Many newer kinds of circuit breakers also open an overloaded circuit faster than a fuse can. For these reasons, all newer buildings use circuit breakers instead of fuses. Slide39

A

circuit panel

has a circuit breaker for each circuit in the building. The directory on the door of the panel describes what appliances or electric outlets are connected to each circuit.

The directory also tells you how much current each circuit can carry safely.Slide40
Slide41

For the following drawings, add up the current that each appliance uses to see if it will blow or trip the circuit.