Unit 4 - Topic 7

Question 1

Transformers

Answer 1

Used to “step up” voltage for efficient transmission

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

Question 2

Power meter location

Answer 2

Mounted on outside wall of buildings where distribution lines enter

Question 3

Power meter function

Answer 3

Records total electric energy supplied to electric devices operating in house

Question 4

Service panel

Answer 4

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

Question 5

Circuit breaker function

Answer 5

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

Question 6

Circuit breaker internal workings

Answer 6

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

Question 7

Fuse

Answer 7

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

Question 8

Circuit breaker pro vs fuse

Answer 8

Fuses need to be replaced unlike bimetallic strip

Question 9

Fuse usage

Answer 9

Not in minders buildings

Common in electric stoves and automobile electrical systems

Question 10

Order of electricity flow to home

Answer 10

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

Question 11

Branch circuit

Answer 11

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

Question 12

Why branch circuits connected in parallel

Answer 12

Other appliances and devices plugged in will continue to operate

Question 13

Two live wires

Answer 13

Neutral and hot wire

Question 14

Neutral wire

Answer 14

White insulated wire

Question 15

Hot wire

Answer 15

Black insulated wire

Question 16

Ground wire

Answer 16

Bare copper/covered in green insulation

Question 17

Ground wire

Answer 17

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

Question 18

120 V vs 220-240 V usage

Answer 18

Circuits for lamps and ordinary appliances
Vs
Kitchen ranges

Question 19

Electrical code

Answer 19

Set of standards for electrical work

Question 20

Digital electronic technology

Answer 20

Machines that process numerically coded information

Question 21

Binary code

Answer 21

Sequence of “on” and “off” signals

Question 22

Transistors

Answer 22

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

Question 23

Sure suppressors/protectors

Answer 23

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

Question 24

Surge causes

Answer 24

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

Question 25

Power

Answer 25

Energy per unit time

Question 26

Electric power

Answer 26

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

Question 27

``` Symbols: Power Voltage Current Energy Time ```

Answer 27

``` P V I J t ```

Question 28

Power equations

Answer 28

``` P = E/t P= IV ```

Question 29

Watt

Answer 29

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

Question 30

Kilowatt hour (kWh)

Answer 30

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

Question 31

Power rating

Answer 31

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

Question 32

EnerGuide labels

Answer 32

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

Question 33

Larger number of EnerGuide labels

Answer 33

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

Question 34

Coloured bar on EnerGuide labels

Answer 34

Shows how particular appliance compares to others on the market

Question 35

Numbers in bar for EnerGuide labels

Answer 35

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

Question 36

Input energy vs useful output energy

Answer 36

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

Question 37

Efficiency equation

Answer 37

Efficiency = useful output energy/input energy x 100 %

Question 38

Input energy equation is

Answer 38

Same as normal energy equation

Question 39

Incandescent light bulbs

Answer 39

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

Question 40

Halogen Bulbs

Answer 40

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

Question 41

Fluorescent tubes

Answer 41

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

Question 42

Indoor electric safety rules

Answer 42

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

Question 43

Outdoor electric safety rules

Answer 43

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

Question 44

Why extreme caution needed with electricity

Answer 44

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