BT-105 Engineering Graphics - Nov 2022 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aAn area of $144\text{ sq cm}$ on a map represents an area of $36\text{ sq km}$ on the field. Find the RF of the scale of the map and draw a diagonal scale to show km, hectometres and decametres and to measure up to $10\text{ km}$. indicate on the scale a distance $7\text{ km}$, $5\text{ hectometres}$ and $6\text{ decimeters}$.
   How to answer

   • Calculate RF: $\sqrt{144\text{ cm}^2 / 36\text{ km}^2} = 12\text{ cm} / 6\text{ km} = 1/50000$
   • Calculate length of scale: $L = \text{RF} \times \text{Max Length} = (1/50000) \times 10\text{ km} = 20\text{ cm}$
   • Construct diagonal scale of length $20\text{ cm}$ divided into 10 main divisions (each representing $1\text{ km}$)
   • Subdivide first division into 10 parts for hectometres, and vertically divide into 10 parts for decametres
   • Mark the specified distance: $7\text{ km}$, $5\text{ hm}$, $6\text{ dam}$
2. 7 Marks
   bConstruct a conic when the distance of its focus from its directrix is equal to $50\text{ mm}$ and its eccentricity is $2/3$. Name the curve; mark its major axis and minor axis. Draw a tangent at any point, P on the curve.
   How to answer

   • Identify the conic as an ellipse since eccentricity $e = 2/3 < 1$
   • Draw directrix $DD'$ and axis perpendicular to it; locate focus $F$ at $50\text{ mm}$ from directrix
   • Divide $VF:VC = 2:3$ to locate vertex $V$
   • Construct the curve by finding points with ratio of distance from focus to directrix equal to $2/3$
   • Mark the major and minor axes
   • Construct tangent and normal at arbitrary point $P$ using the focus-directrix property
3. 7 Marks
   aThe length of the front view of a line CD which is parallel to HP and inclined $30^\circ$ to VP is $50\text{ mm}$. The end C of the line is $15\text{ mm}$ in front of VP and $25\text{ mm}$ above HP. Draw the projections of the line and find its true length.
   How to answer

   • Draw reference line $xy$
   • Locate $c'$ at $25\text{ mm}$ above $xy$ and $c$ at $15\text{ mm}$ below $xy$
   • Since line is parallel to HP, its front view is parallel to $xy$, length $c'd' = 50\text{ mm}$
   • Draw projector from $d'$
   • Top view is inclined at $30^\circ$ to $xy$ (VP) starting from $c$; locate $d$ on projector of $d'$
   • Measure true length $cd = c'd' / \cos(30^\circ) = 50 / \cos(30^\circ) \approx 57.74\text{ mm}$
4. 7 Marks
   bA line PS $65\text{ mm}$ has its end P, $15\text{ mm}$ above the HP and $15\text{ mm}$ in front of the VP. It is inclined at $55^\circ$ to the HP and $35^\circ$ to the VP. Draw its projections.
   How to answer

   • Notice $\theta + \phi = 55^\circ + 35^\circ = 90^\circ$, line lies in a profile plane
   • Mark $p'$ at $15\text{ mm}$ above $xy$ and $p$ at $15\text{ mm}$ below $xy$
   • Draw true length $65\text{ mm}$ at $55^\circ$ to $xy$ to find locus of $s'$, and at $35^\circ$ to $xy$ to find locus of $s$
   • Determine apparent lengths / project to loci to get front view $p's'$ and top view $ps$
   • Show both views on a single common projector perpendicular to $xy$
5. 7 Marks
   aDraw the projections of a pentagonal prism of base $25\text{ mm}$ side and $50\text{ mm}$ long. The prism is resting on one of its rectangular faces in HP with its axis inclined at $45^\circ$ to HP.
   How to answer

   • Stage 1: Assume prism resting with rectangular face on HP and axis perpendicular to VP (or parallel to HP)
   • Draw true shape of base (regular pentagon of side $25\text{ mm}$) with one side in $xy$
   • Project the top view showing rectangular faces of length $50\text{ mm}$
   • Stage 2: Tilt the prism/axis such that the axis makes $45^\circ$ with HP
   • Project the final front view and top view with proper hidden and visible lines
6. 7 Marks
   bDraw the isometric view of a hexagonal prism having side of base $25\text{ mm}$ and axis $65\text{ mm}$ long resting on its base on HP.
   How to answer

   • Enclose regular hexagon of side $25\text{ mm}$ into a rectangle in orthographic view
   • Draw isometric axes at $30^\circ$ to horizontal and vertical axis
   • Transfer rectangular box dimensions onto isometric plane for base and top face at height $65\text{ mm}$
   • Locate corners of hexagonal base and top using box coordinates
   • Join corresponding corners to show vertical edges and complete isometric view with visible and hidden lines
7. 7 Marks
   aA right circular cone of axis height $80\text{ mm}$ is resting on one of its generators in HP. Draw its projections. The base is $40\text{ mm}$ dia.
   How to answer

   • Stage 1: Assume cone resting on base on HP; draw base circle ($\phi 40$) in top view and triangle ($h=80$) in front view
   • Calculate slant height / generator length: $\sqrt{80^2 + 20^2} \approx 82.46\text{ mm}$
   • Stage 2: Tilt front view so that one generator lies on $xy$ line
   • Project downward from tilted front view and across from initial top view to obtain the final top view (elliptical base with apex)
8. 7 Marks
   bGive some examples where the layering concept is useful to use.
   How to answer

   • Define CAD layers as transparent overlays used to organize drawing entities
   • Example 1: Architectural drafting (walls, doors/windows, electrical layout, plumbing, text on separate layers)
   • Example 2: Mechanical engineering drawings (object lines, hidden lines, center lines, dimensions, hatching)
   • Example 3: PCB/Circuit design (top copper layer, bottom copper, silkscreen, solder mask)
   • Benefits: Controlling visibility, locking/freezing, assigning color/linetype/lineweight systematically
9. 7 Marks
   aName and explain five edit commands used in CAD.
   How to answer

   • 1. TRIM: Cuts entities at edges defined by other cutting objects
   • 2. EXTEND: Lengthens objects to meet the edges of other objects
   • 3. FILLET: Rounds or fillets the edges of two intersecting lines with a specified radius
   • 4. CHAMFER: Creates a beveled edge between two non-parallel intersecting lines
   • 5. OFFSET: Creates concentric circles, parallel lines, and parallel curves at a specified distance
10. 7 Marks
    bExplain the various advantages of CAD.
    How to answer

    • Higher productivity and faster turnaround time compared to manual drafting
    • Superior accuracy and reduction in errors
    • Easy editing, revision, and reusing of standard templates/blocks
    • Enhanced visualization with 3D modeling and rendering capabilities
    • Integration with CAM/CAE for analysis and direct manufacturing
    • Convenient storage, retrieval, and digital sharing
11. 7 Marks
    aWhat is the use of UCS icon? Explain in detail.
    How to answer

    • Definition of User Coordinate System (UCS) vs World Coordinate System (WCS)
    • Role of UCS icon: Visual indicator of current origin (0,0,0) and orientation of X, Y, and Z axes
    • Indication of working plane (XY plane) for 2D/3D drawing operations
    • Modes of UCS icon: At origin vs non-origin display
    • Customization and command controls (UCSICON command: ON, OFF, Origin, NoOrigin)
12. 7 Marks
    bWrite about Dialog boxes and windows in CAD software.
    How to answer

    • Definition and purpose of Dialog Boxes: Interactive graphical interfaces to input settings, parameters, and options (e.g., Layer Properties, Dimension Style, Plot dialog)
    • Components of dialog boxes: Text fields, drop-down menus, checkboxes, radio buttons, preview areas, OK/Cancel buttons
    • Types of Windows in CAD: Drawing window/canvas, Command line window, Tool palettes, Property inspector window
    • Advantages of graphical dialogs over purely text-based command-line inputs
13. 7 Marks
    aExplain the various commands used for transformation of an object. i) Move ii) Copy iii) Rotate iv) Mirror
    How to answer

    • MOVE: Translates an object from a base point to a specified second point without duplicating
    • COPY: Duplicates selected objects from a base point to one or multiple destinations
    • ROTATE: Rotates an object around a specified base point by an angle or reference
    • MIRROR: Creates a reverse duplicate of an object across a specified mirror line with option to delete source object
14. 7 Marks
    bExplain the different methods used for drawing a circle in AutoCAD.
    How to answer

    • 1. Center, Radius: Specify center point and enter radius value
    • 2. Center, Diameter: Specify center point and enter diameter value
    • 3. 2-Point (2P): Specify two endpoints of the diameter
    • 4. 3-Point (3P): Specify any three points on the circle's circumference
    • 5. Tangent, Tangent, Radius (TTR): Select two tangent objects and specify a radius
    • 6. Tangent, Tangent, Tangent (TTT): Select three objects tangent to the circle
15. 14 Marks
    Write short notes of the following. i) Isometric projection ii) Epicycloid iii) Basic drawing command
    How to answer

    • Isometric projection: Axonometric projection where the three coordinate axes appear equally foreshortened at $120^\circ$; isometric scale factor is $\sqrt{2/3} \approx 0.816$
    • Epicycloid: Locus of a point on the circumference of a generating circle rolling without slipping on the outside of a directing/base circle; mention equation/sketch
    • Basic drawing commands in CAD: LINE, POLYLINE, CIRCLE, ARC, RECTANGLE, POLYGON, ELLIPSE with primary syntax and options