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Science 9 > Unit 4 - Topic 7 > Flashcards

Unit 4 - Topic 7 Flashcards

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1
Q

Transformers

A

Used to “step up” voltage for efficient transmission

Used to “step down” voltage to the 240/120 V used in homes and factories

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2
Q

Power meter location

A

Mounted on outside wall of buildings where distribution lines enter

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3
Q

Power meter function

A

Records total electric energy supplied to electric devices operating in house

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4
Q

Service panel

A

Wires from meter connected to main circuit breaker at top of panel
Lower part contains additional circuit breakers for each branch circuit in home

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5
Q

Circuit breaker function

A

Acts as switch and safety device that can cut of all power coming into home

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6
Q

Circuit breaker internal workings

A

Current exceeds safe level
Bimetallic strip inside breaker heats up and bends
Opens up circuit
Current stops flowing until breaker cools
Reset then

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7
Q

Fuse

A

Contains metal conductor which melts when excessive current heats it up
Opens it unit until fuse replaced

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8
Q

Circuit breaker pro vs fuse

A

Fuses need to be replaced unlike bimetallic strip

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9
Q

Fuse usage

A

Not in minders buildings

Common in electric stoves and automobile electrical systems

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10
Q

Order of electricity flow to home

A

Transformer -> power lines -> meter -> service panel -> main circuit breaker

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11
Q

Branch circuit

A

Supplies power to one or more wall plugs or lights connected in parallel by cables in house walls

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12
Q

Why branch circuits connected in parallel

A

Other appliances and devices plugged in will continue to operate

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13
Q

Two live wires

A

Neutral and hot wire

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14
Q

Neutral wire

A

White insulated wire

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15
Q

Hot wire

A

Black insulated wire

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16
Q

Ground wire

A

Bare copper/covered in green insulation

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17
Q

Ground wire

A

Reduces shock hazards by safely channeling back into ground any current that has “leaked” onto metal components in electric circuit

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18
Q

120 V vs 220-240 V usage

A

Circuits for lamps and ordinary appliances
Vs
Kitchen ranges

19
Q

Electrical code

A

Set of standards for electrical work

20
Q

Digital electronic technology

A

Machines that process numerically coded information

21
Q

Binary code

A

Sequence of “on” and “off” signals

22
Q

Transistors

A

Solid-state components that can be turned on and off by electric signals

23
Q

Sure suppressors/protectors

A

Suppressor absorbs some of electric surge and deserts ret to ground
Often used to protect expensive electronic equipment

24
Q

Surge causes

A

Lightning
Turning on or off large appliances
Local power company transferring large amounts of electricity into or out of power grid

25
Q

Power

A

Energy per unit time

26
Q

Electric power

A

Describes amount of electric energy converted into other forms of energy every second
Describes amount of electric energy transferred from one place to another in certain amount of time

27
Q 
Symbols:
Power
Voltage
Current
Energy
Time
A 
P
V
I
J
t
28
Q

Power equations

A 
P = E/t
P= IV
29
Q

Watt

A

Unit for power
Kilowatts (kW) = 1000 W
Megawatts (MW) = 1 000 000 W
Gigawatts (GW) = 1 000 000 000 W

30
Q

Kilowatt hour (kWh)

A

1 kWh is total energy supplied to a 1000 W load during 1 h of operation
Customary unit
Non-SI

31
Q

Power rating

A

Tells how many joules of energy specific device uses in every second of operation

32
Q

EnerGuide labels

A

Help ppl make comparisons of energy use when purchasing large home appliances

33
Q

Larger number of EnerGuide labels

A

Approx amount of energy appliance will use in one yr of typical operation

34
Q

Coloured bar on EnerGuide labels

A

Shows how particular appliance compares to others on the market

35
Q

Numbers in bar for EnerGuide labels

A

Give Troy use of most efficient(left end) and least(right end) appliances of similar type

36
Q

Input energy vs useful output energy

A

Amount of electric energy taken in
Vs.
Amount of electric energy used

37
Q

Efficiency equation

A

Efficiency = useful output energy/input energy x 100 %

38
Q

Input energy equation is

A

Same as normal energy equation

39
Q

Incandescent light bulbs

A

5 % efficient
Most electric lighting in homes largely provided by it
About 95 % of electric energy is converted to waste heat as current passes through thin metal filament coiled inside bulb

40
Q

Halogen Bulbs

A

15 % efficient
Filled with high-pressure gas w/ traces of iodine(helps prevent filament from evaporating)
Bulbs can operate at high temps so convert greater proportion of input energy into light
Can be fire hazard
Last 2-6x longer than incandescent bulbs

41
Q

Fluorescent tubes

A

20 % efficient
Contains gas (mercury vapour) which emits energy when current passed through
White material on inside of glass glow cuz of that
Operate at low temps so waste very little energy as heat
Last 10-13x longer than incandescent bulbs
More expensive
Reduce environmental impact

42
Q

Indoor electric safety rules

A

Don’t overload an outlet/circuit by plugging in too many electric devices
Never work on or clean appliances that r still plugged in
Replace frayed or worn electric cords
Use receptacle covers on easily accessible outlets
Never use appliances close to sink or bathtub with water in it or when hands r wet

43
Q

Outdoor electric safety rules

A

Never allow body or something ur holding to come into contact w/ live electric wires
Never use ungrounded or frayed two-prong electric cords outdoors
Don’t operate electric equipment outside when raining
Before digging, ensure no underground utility cables

44
Q

Why extreme caution needed with electricity

A

Heart failure at 1 A and average household carries max current of 15 A

Science 9 (21 decks)

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