electrical circuits part A

Question 1

equipment lighting is used to provide

Answer 1

vision during night operation. machine operator safety . operator convenience . unit appearance

Question 2

battery group disconnect switch

Answer 2

will prevent accidental slow discharge of battery group when unit is in park and not operating . can be connected in series with negative or positive battery leads

Question 3

circuit protection devices

Answer 3

fuses and breaker panels . prevent machines electrical components from being destroyed by large current flows

Question 4

main circuit protection device

Answer 4

usually 60 to 80 amps . protect entire machines electrical circuits . connected in series to machine fuse breaker box

Question 5

type 1 circuit breaker

Answer 5

used when electrical current flow needs to be restored quickly . circuit opens and closes when a bimetal strip heats up and cools down . headlight circuits would use this type

Question 6

type 2 circuit breaker

Answer 6

come equipped with a heat -producing resistor . this resistor holds the circuit breaker in the off ( open) position while the breaker rating is exceeded . used in non critical circuits like interior cab lighting

Question 7

type 3 circuit breaker

Answer 7

have a manual reset button . can be used in non critical circuits that can remain non energized until the circuit is manually reset . used in equipment mounted signage

Question 8

how do you properly size a circuit protection device

Answer 8

P = I x E or watts = amps x volts

Question 9

high beam head lamps produce what for wattage

Answer 9

high wattage usually 80 watts

Question 10

low beam lights produce what for wattage

Answer 10

low wattage usually 60 watts

Question 11

flood / working lamps are connected where in the electrical circuit

Answer 11

connected into the key switch controlled circuits

Question 12

why do you want flood / working lamps to be connected into the key switch control circuit

Answer 12

so you wont drain your battery when the unit is shut off

Question 13

tail lamps are used for

Answer 13

used to outline a machines perimeter in poor visibility conditions . always red in color

Question 14

clearance lamps are used for what

Answer 14

used to indicate the outer sides of a unit . usually amber in color

Question 15

panel lighting

Answer 15

assists the operator in viewing the panel gauges . controlled by the master switch . able to alter the intensity of the light with the use of a lamp dimming solid state module

Question 16

another way to dim panel lights other than a solid state module is by using a

Answer 16

series connected rheostat

Question 17

why is it important to mount a rheostat away from flammable material

Answer 17

because the heat developed from the rheostat may start a fire

Question 18

what is pulse width modulation

Answer 18

a digital signal that turns the circuit voltage on and off

Question 19

what is duty cycle

Answer 19

the period of time a pulse width modulating signal is on compared to off

Question 20

fiber optic cable is made out of what

Answer 20

plastic core surrounded by a polymer optical cladding sheath

Question 21

when fiber optical cables fail what is the most likely source of the problem

Answer 21

the light source has malfunctioned

Question 22

if the fiber optic cable is damaged you must

Answer 22

replace the cable . it cannot be repaired

Question 23

when retrofitting break lights to LED you must also change

Answer 23

electromechanical flasher must be changed to a solid state electronic flasher

Question 24

if you are going to use a electromechanical flasher with LED lights you must

Answer 24

install a series connected resistor

Question 25

what are warning beacons

Answer 25

safety devices mounted at the highest point of the unit

Question 26

when warning beacons fail they must be replaced as

Answer 26

a unit

Question 27

what circuit is the warning beacon connected into

Answer 27

the key switch control . beacon will operate when the engine is operating

Question 28

if the ECU is the control device for back up warning lights the relay must be

Answer 28

grounded through the ECU

Question 29

what does it mean to have multiple switches control your cab lights

Answer 29

it means that any one switch can turn your lights on or off . ex both doors or switch on the dash

Question 30

what is the normal state of a door switch that controls the cab lights

Answer 30

normally closed

Question 31

LED lamps require approximately how much of the electrical current to that of a normal incandescent bulb

Answer 31

1/10

Question 32

what is the advantage of LED stop lights

Answer 32

to provides a quicker reaction time for drivers to respond

Question 33

DC motors use electricity and magnetism to produce

Answer 33

rotary mechanical motion

Question 34

what are the two types of DC motor configurations

Answer 34

permanent magnet . parallel wound

Question 35

what is the only factor that limits a PM motors armature speed

Answer 35

counter electromagnetic force ( CEMF )

Question 36

if an equipment demads a slower slower rotation that the rated speed of the PM motor can provide you must

Answer 36

install a gear box reduction to the motors armature

Question 37

the direction a PM motor turns depends on

Answer 37

the interaction between the magnetic lines of force around the field coils and the direction lines of force around the armature windings

Question 38

how can you protect the wiring harness if the engine is cranked with the battery disconnect in the open position in accessory that requires constant power memory

Answer 38

install positive and negative leads uses in both

Question 39

when testing electrical circuits you should always use

Answer 39

high impedance meter . ( 10m ohms )

Question 40

when replacing speakers you should always

Answer 40

match the replacement speaker two the output of the systems amplifier

Question 41

when cutting speaker wires with side cutters what may happen to the output amplifier

Answer 41

you may cause a short between the two lines through the side cutters

Question 42

what is one way to reduce static noise or interference

Answer 42

install a series coil ( filter choke ) or a parallel capacitor to the machines power lead or at the source

Question 43

when connecting intermediate grounds what should you make sure they are all connected to

Answer 43

the main ground ( cab must have a ground strap to the units main frame

Question 44

what is the park position on the widow wipers circuit

Answer 44

park contacts supply current to the motor after the wiper switch has been turned off . this allows the wipers to keep running until park position has been reached

Question 45

windshield wiper motors are

Answer 45

two speed DC motors

Question 46

are the internal components of windshield wiper and washer systems serviceable

Answer 46

no . they must be replaced

Question 47

what would use an armature connected to a diaphragm that causes a column of air to vibrate at a frequency

Answer 47

a horn

Question 48

in a relay what contacts are normally open

Answer 48

30 to 87

Question 49

in a relay what contacts are normally closed

Answer 49

30 to 87A

Question 50

in a relay what contacts carry large current

Answer 50

85 to 86

Question 51

what would happen to a warning light if the voltage on both sides of the light were the same

Answer 51

the light would be electrically balanced and not illuminate

Question 52

why do some manufactures install a resistor in parallel on a warning light

Answer 52

because if the bulb were to burn out and go open it would not shut down the entire circuit

Question 53

what is EEPROM

Answer 53

electronically erasable programable read only memory

Question 54

if a temp gauge uses a negative temperature coefficient thermistor . the resistance of the thermistor would read high when

Answer 54

the temp was cold . resistance lowers when temperature increases

Question 55

what are the two types of gauges that can be used to determine the condition of the equipments electrical condition

Answer 55

ammeter or voltmeter

Question 56

the intensity of the insterment panel lamps can be controlled by the use of

Answer 56

series connected rheostat or pulse width modulated signal

Question 57

the turn signal light circuit has a turn signal flasher connected in its circuit . how would the flasher be connected

Answer 57

series with the turn signal lamp connection

Question 58

what other electrical accessory can be controlled by the same switching system that controls the back up lamp circuit

Answer 58

the backup alarm

Question 59

equipment tracking systems are comprised of what two distinct components

Answer 59

GPS and digital satellite uplink

Question 60

anti theft systems can be classed as either

Answer 60

alarm or theft deterrent