Engineering - Exam Papers - HL - Paper - 1994

300 Marks
Answer Question 1, Sections A and B and FOUR other questions.

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1.
(100 Marks)
Section A - 50 Marks
Give brief answers to any ten of the following :
(a) Give an example of the narcotic effect of a toxic material.
(b) Distinguish between gravity concentration and flotation in ore dressing.
(c) State two ways in which electronic components can be protected when being connected into circuits.
(d) Identify clearly the process used to manufacture any two of the following :
(i) Car body panel;
(ii) Plastic pedal bin;
(iii) Brass letter box.
(e) State two factors that affect the creep behaviour of metals.
(f) Why is zinc considered to be a good choice in protecting steel against corrosion?
(g) What is the difference between a vacancy and a dislocation?
(h) Discuss the influence of bond type on the electrical properties of graphite.
(i) What factors should be considered when joining materials using adhesives?
(j) What is age hardening?
(k) Differentiate between 8 Mb and 4 Mb of computer RAM.
(l) Identify the pneumatic symbols (i) and (ii) shown.
(i)
(ii)
(m) Indicate the contribution of any one of the following technology?
(i) Jean-Louis Poiseuille;
(ii) Thomas Seebeck;
(iii) Thomas Newcomen.
Section B - 50 Marks
Answer all of the following :
(n) What is the difference between an input and output transducer? Give an example of each type.
(o) Identify any three of the following transducers shown by the symbols (a) to (e) and state the function of each one.
(a)
(b)
(c)
(d)
(e)
(p) State three factors which should be considered in a specification for a transducer.
(q) Explain the principle of operation of one of the following transducers:
(i) piezoelectric transducer;
(ii) strain gauge;
(iii) thermocouple
(r) State two factors which influence transducer performance.
2.
(50 Marks)
(a) (i) What basic information can be obtained from a tensile test?
(ii) State two factors which cause different types of fracture of the specimen.
(b) The following results were obtained from a tensile test on a material of diameter 10mm and gauge length 50mm.
LOAD (kN) 25 50 75 100 110 130 150 175 190 198 195 180
EXTENSION (mm) 0.15 0.20 0.35 0.42 0.52 1.10 2.20 4.20 6.00 8.00 11.00 14.00
Plot the load-extension graph and determine:
(i) the tensile strength;
(ii) 0.1% proof stress;
(iii) Young's Modulus.
(c) Why are non-destructive tests widely used in industry? Describe one test suitable for the detection of internal flaws.
3.
(50 Marks)
(a) Define two of the following terms:
(i) ferrite;
(ii) austentite
(iii) cementite
(iv) pearlite
Draw an iron-carbon diagram and indicate clearly the above phases.
(b) (i) Explain why a 0.7% carbon steel is hardened if quenched rapidly from 900°C.
(ii) Differentiate between eutectic and eutectoid reactions, stating any temperature and structural changes.
(c) Answer any two of the following:
(i) Differentiate between carburising and nitriding;
(ii) Explain what is meant by a controlled atmosphere furnace;
(iii) What are the effects of alloying chromium and nickel with steel?
4.
(50 Marks)
(a) State two ways in which the movement of dislocations in a material may be restricted.
(b) The melting points of cadmium and bismuth are 321°C and 268°C respectively. The given table shows the solidification temperatures for various alloys of the two metals.
Amount of cadmium in alloy (%) 10 20 30 40 50 60 70 80 90
Temperature at the beginning of solidification (°C) 237 205 175 140 190 235 265 290 310
Temperature at the end of solidification (°C) 140 140 140 140 140 140 140 140 140
Using the graph paper supplied, draw the thermal equilibrium diagram according to the given data and label the diagram fully.
(c) Determine from the diagram, for a 70% cadmium alloy;
(i) the composition of the phases present at 210°C;
(ii) the ratio of solid to liquid at 170°C.
5.
(50 Marks)
(a) (i) State two functions of the electrode coating in manual metal arc welding.
(ii) State one factor to be considered in preparing a joint for welding.
(b) Describe, with the aid of a diagram, a manual metal arc welding circuit operating from a 220V ac power supply
Explain how such a circuit operates when supplying direct current for welding.
(c) Describe, with the aid of a diagram, the main features, operation and application of one of the following processes.
(i) Metal inert gas welding;
(ii) seam welding
OR
(c) Explain one of the following in relation to robotic control welding:
(i) walk-through (or lead-through) method of programming robots;
(ii) Actuation methods used to control robot movement.
6.
(50 Marks)
(a) (i) Distinguish between crystalline and amorphous structure in materials.
(ii) State the function of any two of the following in relation to polymers:
- plasticisers;
- fillers;
- stabilisers.
(b) Sketch cross-linked, branched and linear polymer structures.
In the case of these structures:
(i) state the polymerisation process used;
(ii) describe the bonds in the molecular chains;
(iii) state the significance of the type of bonding between adjacent chains.
(c) (i) What factors influence the choice of a plastics moulding process?
(ii) Describe, using a diagram, the principle of injection or extrusion moulding.the composition of the phases present at 210°C;
7.
(50 Marks)
(a) State
(i) three requirements of a machine tool, e.g. a lathe, and
(ii) three advantages of using a cutting fluid in a machining process.
(b) Describe with the aid of a diagram, the principal of operation of any one of the following:
(i) permanent magnetic chuck;
(ii) dividing head;
(iii) dial indicator.
(c) (i) Write down an expression for tool life and hence state the factors which influence tool life.
(ii) Determine the metal removal rate in mm3/min given that:
cutting speed = 40 m/min
depth of cut = 4mm
feed rate = 0.2 mm/rev
OR
(c) (i) What are the advantages of CNC machining?
(ii) In relation to program features, distinguish between a canned cycle and a program loop.
8.
(50 Marks)
(a) Describe the principal function of any three of the following:
(i) heat pipe;
(ii) universal joint;
(iii) bimetallic contact breaker;
(iv) light-dependant resistor;
(v) flow regulator.
(b) Explain clearly the function of any two of the following:
(i) transistor;
(ii) shuttle valve;
(iii) ratchet and pawl mechanism.
(c) Explain, with the aid of a diagram, a method of opening a door automatically.
OR
(c) Identify the components A,B,C,D and E in the given circuit diagram.
State the function of such a circuit.