Whole Revision Guide Part 2

Question 1

How are PCBs made consistent?

Answer 1

keep exposure time the dame so that the same amount of copper is removed from the board

Question 2

What are reference points?

Answer 2

a point where measurements are made from
they help control accuracy
they are important in aligning CAM machines and when scaling the size of something

Question 3

name 3 production aids

Answer 3

templates, patterns, jigs and reference points

Question 4

what do jigs do?

Answer 4

guides tools, can be specifically made for a job, they speed up production and simplify the making process

Question 5

what are short length and long length fibres called?

Answer 5

staple and filament

Question 6

What are the three categories for fibres

Answer 6

natural, regenerated, synthetic

Question 7

what are regenerated fibres?

Answer 7

natural fibres that have been chemically treated

like viscose fibres

Question 8

how are viscose fibres made?

Answer 8

cellulose is dissolved in sodium hydroxide solution. the liquid is forced through tiny holes and hardened to form filament fibres. filaments are stretched into yarns

Question 9

what is steel often used for?

Answer 9

vehicle parts, like brake disks, engine, wheels and drive shaft. durable vehicle parts can be made relatively cheaply and easily. car bodies are also made from steel as they are designed to crumple and absorb impact

Question 10

what is aluminium used for in motor vehicles

Answer 10

corrosion resistant car body parts instead of steel. it’s less dense so improves acceleration and fuel economy. it’s more expensive

Question 11

Why are electrically conductive strips used in cars?

Answer 11

they are on the inside of the rear window to defog it and clear the glass by heating up

Question 12

what conditions do engine electronics need to withstand?

Answer 12

high temperatures and freezing conditions

Question 13

what does a drive belt do in a washing machine?

Answer 13

transmits rotary motion to the spinning drum. they are often made from rubber or a polyurethane plastic because they are strong and flexible

Question 14

what is a heating element?

Answer 14

a wire that gets hot when a current passes through it, caused by electrical resistance. often made from a nickel-chromium alloy as it has a high melting point

Question 15

what do photosensitive materials do?

Answer 15

respond to being exposed to light, like photographic film and light dependent resistors. photoetching is used to etch designs onto PCBs

Question 16

how is aluminium oxide different to rust?

Answer 16

it sticks strongly to the fresh aluminium and protects it from further corrosion.

Question 17

what is anodisation?

Answer 17

anodisation thickens the protective oxide using electric current. anodised aluminium is used to make aircraft parts, pans and window frames

Question 18

what do current and voltage ratings do?

Answer 18

prevent damage to components by informing the user what current and voltage the appliance is supposed to work at.

Question 19

what do resistors do?

Answer 19

they reduce the current in a circuit. a greater resistance than needed is safer

Question 20

what do bands 1 and 2 on a resistor indicate?

Answer 20

the first two digits of the resistance

Question 21

what does band 3 on a resistor do?

Answer 21

indicates how many zeroes that come after the first two digits

Question 22

what does band 4 on a resistor do?

Answer 22

represents the tolerance. an E12 resistor will have a silver band 4, representing 10% tolerance

Question 23

what is a Dual In Line package?

Answer 23

one of the ways ICs are packaged. the circuit is placed in a rectangular protective casing made of plastic/ ceramic. metal legs stick out of the casing in two parallel rows.

Question 24

How can ICs be attached to a circuit?

Answer 24

soldered through hole, or plugged into an IC socket making them easier to replace

Question 25

what is a PIC?

Answer 25

a specific type of microcontroller. they are programmable intelligent computers. most have flash memory. different PICs have different amounts of memory and pins.

Question 26

what are chains and what do they do?

Answer 26

roller chains are metal links pinned together to form a loop. they transfer rotary motion from one sprocket to another

Question 27

what are gears and what do they do?

Answer 27

they can have different number of teeth and tooth shapes

Question 28

what are the two types of spring you can buy?

Answer 28

compression (resist compression), and extension (resist extension)

Question 29

what is spring rate?

Answer 29

how easy the spring is to stretch or compress

Question 30

What does CNC stand for?

Answer 30

computer numeric control. CAM machines use this and involves using the precise coordinates to control where the laser cuts

Question 31

what do PCB drills do?

Answer 31

cut holes in PCBs so that pins or wires can be pushed through. very thin drill bits are used.

Question 32

How is soldering done in mass production?

Answer 32

flow soldering. this is when the PCB is passed over a pan of molten solder. A pump produces an upwelling to solder in place.