POST 1: MATERIALS TECHNOLOGY & MANUFACTURING PROCESSES

(From Page 1 and Page 2)

Mechanical Engineering & Material Science Practice Questions

PART A: MULTIPLE CHOICE QUESTIONS

Question 1

The operation in Figure 1 is called:

(Refer to Figure 1 in image_5fb6dc.jpg — showing a tool rotating inside a hole while the work remains stationary)

• A. Drilling

• B. Reaming

• C. Boring

• D. Counter boring

Question 2

Identify the metal with the lowest melting point.

• A. Tin

• B. Copper

• C. Lead

• D. Mercury

Question 3

Plastics are made from the following EXCEPT:

• A. petroleum

• B. coal

• C. ores

• D. gases

Question 4

The Izod and the Charpy tests are performed for determining:

• A. stress and strain of a metal

• B. impact strength of material

• C. endurance strain

• D. resistance to failure

Question 5

Given: $\text{force} = 35.7\text{ kN}$, $\text{area} = 25\text{ mm}^2$, $\text{gauge length} = 28\text{ mm}$, and $\text{Extension} = 0.2\text{ mm}$. What is the value of the stress?

• A. 14.28

• B. 1.428

• C. 142.8

• D. 1428

Question 6

Identify the moulding process shown in Figure 2:

(Refer to Figure 2 in image_5fb6dc.jpg — showing plaster slurry being poured over a pattern)

• A. Bench moulding

• B. Pit moulding

• C. Floor moulding

• D. Plaster moulding

Question 7

The double-Vee butt weld is used for the welding plates of thickness over:

• A. $10\text{ mm}$

• B. $5\text{ mm}$

• C. $13\text{ mm}$

• D. $0.3\text{ mm}$

Question 8

Soluble oils are used during cutting and machining processes to:

• A. increase the cutting speed

• B. provide a smoother work

• C. remove heat

• D. provide good finishing surface

Question 9

One of the functions of coke in the production of pig iron is to:

• A. play the role of an iron ore

• B. act as a flux and remove impurities in the molten iron as slag

• C. act as a fuel to supply heat for the various chemical reactions

• D. cool the molten iron.

Question 10

The type of crystal structure shown in Figure 3 is called:

(Refer to Figure 3 in image_5fb6dc.jpg — showing a hexagonal unit cell arrangement)

• A. Body-Centered Cubic (BCC)

• B. Face-Centered Cubic (FCC)

• C. Hexagonal-Closed-Pack (HCP)

• D. Body-Hexagonal Closed-Pack (BHP)

PART B: STRUCTURED QUESTIONS

Instructions: Answer any three (03) questions from this section.

1. COMPOSITE MATERIALS

• a) * i. What is a composite material? (1 mark)

  • ii. What is the difference between a composite material and an alloy? (2 marks)

• b) State FOUR (04) properties required from composite materials. (1 mark)

• c) * i. Give TWO (02) functions of a matrix in a composite material. (2 marks)

  • ii. State THREE (03) examples of matrices. (1.5 marks)

• d) Name THREE (03) parts of a car that are made from composite materials. (1.5 marks)

• e) Give TWO (02) methods of repairing parts made from composite materials in a vehicle. (1 mark)

2. CORROSION AND METAL COATING

Figure 1 below shows a metal coating process.

(Refer to Figure 1 in image_5fb682.jpg to view the hot-dip industrial treatment line)

• a) * i. Identify the metal coating process in Figure 1. (1 mark)

  • ii. Give the names of the parts marked 1 and 2. (1 mark)

  • iii. Briefly describe the process in Figure 1. (2 marks)

• b) * i. What is corrosion? (1 mark)

  • ii. Give THREE (03) causes of corrosion. (1.5 marks)

  • iii. Give THREE (03) effects of corrosion. (1.5 marks)

• c) What is the difference between dry corrosion and wet corrosion? (1 mark)

• d) What is the difference between galvanizing and tinning? (1 mark)

3. METAL FORMING PROCESSES

• a) State FOUR (04) metal forming processes. (2 marks)

• b) Write down the various forming processes used to obtain the following parts: (2 marks)

  • i. Crankshaft

  • ii. Gear box housing

  • iii. Connecting rod

  • iv. Electrical wires

• c) Give TWO (02) reasons why most mobile engine components are not moulded. (1 mark)

• d) State FOUR (04) advantages of the use of aluminium to manufacture vehicle parts. (2 marks)

• e) Why can’t aluminium be welded with steel? (1 mark)

• f) With the aid of a sketch, define extrusion. (2 marks)

POST 2: AUTOMOTIVE ELECTRICAL SYSTEMS & ELECTRICAL DIAGNOSTICS

(From Page 3 and Page 4)

SECTION A: LIGHTING AND SIGNALIZATION SYSTEM

(Answer THREE Questions from this section)

1. COMPONENT & SENSOR TESTING

• (a) Copy and fill the table below. Give a brief description of the test method of the listed electronic components. (2.5 marks total — 0.5 mark x 5)

N°	Component	Test method (0.5mark x 5 = 2.5marks)
1	Capacitor
2	Diode
3	Transistor
4	Inductor
5	Resistor

• (b) Copy and fill the table below. Give a brief description of the test method of the listed sensors. (2.5 marks total — 0.5 mark x 5)

N°	Component	Test method (0.5mark x 5 = 2.5marks)
1	Inductive (reluctance)
2	Hall effect
3	Throttle potentiometer
4	Oxygen (lambda)
5	Flap air flow

2. OSCILLOSCOPE WAVEFORM ANALYSIS

The waveforms below are from an oscilloscope showing actual (correct) operating output signals from vehicle electrical and electronic systems.

(Refer to image_5e5148.jpg to view waveforms Figure A, B, C, and D)

• (c) Give the unit scale for the ordinate and the abscissa for the waveforms. (2 marks total — 1 mark x 2)

• (d) Identify the wave forms: (8 marks total — 2 marks x 4)

  • (i) Figure A

  • (ii) Figure B

  • (iii) Figure C

  • (iv) Figure D

3. IGNITION SYSTEM THEORY

• (a) List THREE properties of spark plug electrode material. (3 marks total — 1 mark x 3)

• (b) Give FOUR factors which determine the thermal capacity of a spark plug. (4 marks total — 1 mark x 4)

• (c) Name FOUR base materials used for spark plug electrodes. (2 marks total — 0.5 mark x 4)

• (d) On appendix 2, using a pencil, complete the ignition circuit in Figure 6. (8 marks)

• (e) Patterning to ignition malfunctioning, give THREE possible faults when the engine rotates but does not start. (3 marks total — 1 mark x 3)

POST 3: AUTOMOTIVE APPLIED APPLIED ELECTRICAL CALCULATIONS

(From Page 4)

SECTION B: ELECTRICAL ENGINEERING CALCULATIONS

(Answer TWO Questions from this Section)

Question 6: STARTER MOTOR CIRCUIT DESIGN

The current supplied to the starter motor of an automobile is $160\text{ A}$ when starting the engine. The connecting (supply) cable has a total length of $1.3\text{ m}$ and consists of $15$ strands of wire, each with diameter $1.2\text{ mm}$. The resistivity of the metal used to make the strands is $1.4 \times 10^{-8}\ \Omega\text{m}$.

• (a) Calculate:

  • (i) The resistance of each strand. (3 marks)

  • (ii) The total resistance of the cable. (2 marks)

  • (iii) The power loss in the cable. (2 marks)

• (b) When the starter motor is used to crank the engine, $700\text{C}$ of charge passes through a given cross-sectional area of the cable.

  • (i) Assuming the current supply is constant; calculate the time it took for this charge to flow past the cross-section. (3 marks)

  • (ii) Calculate the amount of electrons that flew past the cross-section, considering an electron has a charge of $-1.6 \times 10^{-19}\text{C}$. (3 marks)

• (c) The E.M.F. of the battery is $13.6\text{V}$ and its internal resistance $0.012\ \Omega$. Calculate:

  • (i) The potential difference across the battery terminals when the current flow is $160\text{A}$. (3 marks)

  • (ii) The power loss as heat by the battery during operation. (2 marks)

  • (iii) What is the total power supplied to the starter motor circuit by the battery? (2 marks)

Question 7: LIGHTING SYSTEM LOGISTICS

• (a) The stop lamp cable of a lorry is $7700\text{ mm}$ long and its nominal cross-sectional area of $0.95\text{ mm}^2$. Calculate:

  • (i) The resistance of the cable at 0°C. (2 marks)

  • (ii) The resistance of the cable at 26°C. (2 marks)

  • (iii) The voltage drop due to cable resistance if a bulb of 12-V / 20W is used in the stop light. (2 marks)