Engineered Products

Question 1

What happened when electricity was introduced to society?

Answer 1

Most duties at home went from being manual labour to having electrical appliances to assist them.

Question 2

What is the transmissibility of forces?

Answer 2

does not matter here strong person is in a tug of war; doesnt matter what order forces are acting in

Question 3

What is the three force axiom?

Answer 3

if three forces are on a body in equilibrium all forces are concurrent (graphical)

Question 4

What are moments? whats the formula? unit?

Answer 4

a turning effect
M=F*d f is force, d is perp. distance
Nm

Question 5

What is a couple? Whats the formula?

Answer 5

two parallel forces of equal magnitude but opposing direction form a ‘couple’ which creates a turning effect.
M=F*d where f is the force and d is distance between them

Question 6

What are ethics?

Answer 6

doing the right thing.

Question 7

Why would we reduce, reuse and recycle? 4

Answer 7

less waste, limited materials, limited energy, ethical

Question 8

What is the difference between hot and cold working?

Answer 8

Hot working is above the recrystallisation temperature, cold working is below it.

Question 9

What happens when a material is cold worked?

Answer 9

equiaxed grains turn elongated; in chemical structure, tangled forest of dislocations –> energy loss –> work hardening

Question 10

What is grain flow?

Answer 10

Grain flow occurs when an object is worked and not cut into shape. It is when the grains are curved to follow the shape of a product, so there are no weak grain boundaries

Question 11

Compare cold working (5) to hot working (4)

Answer 11

Cold - No heat, more force –> bigger machines, no oxides (bright steel), higher hardness and strength, lower malleability and ductility
Hot - heat=money, less force –> smaller machines, oxide layer (black steel), no property change.

Question 12

What are the three phases of recrystallisation of metals after cold working (both names of each stage, and briefly what happens in each stage.

Answer 12

Recovery/stress relieving- nothing really happens; internal residual stresses relieved
Recrystallisation/normalisation - elongated grains –> small equiaxed grains - decreased hardness and strength, increased ductility
Grain Growth/annealing - grains get big, ductility increases

Question 13

What affects the recrystallisation temperature?

Answer 13

the type of metal and how much it has been worked

Question 14

What is heat treatment?

Answer 14

the process of improving/changing the properties of a material (usually metal) by the controlled heating and/or cooling of the material.

Question 15

Heat treatment - what does hardening do?

Answer 15

hardens material

usually stronger but brittle

Question 16

Heat treatment - what does tempering do?

Answer 16

toughening

Question 17

Heat treatment - what does annealing do?

Answer 17

Softening

Question 18

Heat treatment -What is normalising?

Answer 18

refining grain structure e.g. recrustallising elongated grains to remove grain defects

Question 19

What are two ways of changing the properties of metals?

Answer 19

heat treatment, alloying

Question 20

What is an alloy?

Answer 20

a mixture of two or more metals OR a non-pure metal that acts like a metal

Question 21

GENERALLY what does alloying do to strength, hardness, corrosion resisitance and ductility?

Answer 21

increase strength
increase hardness
decrease corrosion resistance
decrease ductility

Question 22

What are 2 other names for voltage? what is it cause by?

Answer 22

voltage or EMF, caused by difference in charge (-ve–>+ve)

Question 23

What are the parts of an engineering report and what they do?

Answer 23

Title page
Abstract - summary of entire report to prevent unnecessary reading
Intro - sets the scene
body
conclusion; recommendation, make a decision
references; for further studies, prevents plagiarism, credibility
appendix; extra information

Question 24

What is Ohms law?

Answer 24

V=IR

Question 25

What is the power formula?

Answer 25

P=IV or P=(I^2)R

Question 26

What are some safety issues of electricity? (3 causes, 2 effects)

Answer 26

Misuse, poor maintenance, overloading
electrical shock of users
fires

Question 27

What are 7 protective features for electricity?

Answer 27

Insulation from current - polymer 
Earth/ground circuit 
Fuse
Circuit breaker
earth leakage detector (ELD)
residual current detector (RCD)
decreasing voltage

Question 28

Explain an earth/ground circuit.

Answer 28

cable connects current to ground, so that electricity will not flow through human? sometimes. note; double insulated products dont need it

Question 29

Explain a fuse.

Answer 29

A thin wire designed for a certain amperage melts away after that amperage and breaks circuit

Question 30

Explain circuit breakers

Answer 30

Magnetism; more electricity generates stronger magnetic field which breaks the circuit; can easily be reset

Question 31

Explain ELD’s

Answer 31

shuts down circuit if ANY current goes to earth (circuit breaker)

Question 32

explain RCDs

Answer 32

measures current through both active and neutral wires; if different shuts off circuit

Question 33

What does connecting batters in parallel do?

Answer 33

no change in voltage, increases battery life.

Question 34

How can you get a strong magnetic field from electricity? 3

Answer 34

more current, solenoid it up, iron core that bitch.

Question 35

What happens if you pass a conductor through a magnetic field? How can you strengthen this effect? 4

Answer 35

you induce a current in the conductor 
stronger magnets
more conductor 
coil the wire
spin it faster

Question 36

What are the advantages of a DC motor? 3

Answer 36

easy to change direction, no reverse gear needed, can be used with AC and DC motors.

Question 37

What are 4 positives of universal motors and the main negative?

Answer 37

variable speed,
lots of poer
everything electromagnet
can run on AC or DC
-ve - arcing brushes create radio interference, ozone, noise

Question 38

How do induction, or Squirrel Cage, motors work?

Answer 38

fluctuating magnetic field induces current in the rotor, –> magnetic field in aluminium rods –> motion from repelling of like poles

Question 39

What are 3 advantages of induction motors, and what are 3 disadvantages?

Answer 39

+ve - ‘indestructible’, low maintenance.

-ve only ac, cannot be made to go faster, as speed depends on Hz, single phase; low torque at start up.

Question 40

how can the low torque of induction motors at start up be fixed?

Answer 40

1 - small electric starter motor

2 - boost startup voltage through capacitor

Question 41

What is rectification and why would it be done? (2)

Answer 41

turning ac into dc, some components are polarized (only work correctly with electricity going in one direction)
voltage varies greatly

Question 42

What is involved in rectifying current? (3 things)

Answer 42

diodes allow current to only flow in one direction, Bridge allows both directions to power(see diagrams), capacitor provides a more stable power source.