20th May 2020, Period 3, Class 11, Engineering Graphics - Orthographic Projection - Revision

Dear Students,

Good Morning and a warm welcome to today's class.

It feels really nice to meet up for yet another class this morning.

We will revise Orthographic projection in today's class.

Orthographic Projection

The word Orthographic consists of two words 'Ortho' and 'Graphic'. 'Ortho' means 'right angles' and 'graphic' means drawing. Therefore, orthographic projection is a drawing in which the lne of sight falls perpendicularly on the Planes of projection.

Projectors

The lines of sight or rays that fall go past the object and falling on the so called 'screens'.

Projection

Projection is the representation of the shape (something similar to the shadow) of the object on a plane (or the screen). If straight lines are drawn from various pointson the contour of the object to meet the plane (screen) the figure so obtained on the plane id called as the projection of he object.

Planes of Projection 

The screen referred above is actually the plane of projection that hosts the figure (or the shadow) of the object.

Refer to Fig 1 below. The object is placed in the first quadrant and its shadow falls on the horizontal and the vertical planes.   






Fig 1: Quadrants of projection. First Angle of projection




Fig 2: Planes of projection or Principal planes



Q 1. A point is placed 50 mm in front of the VP and 20 mm above the HP. Draw its projections.

Q 2. A point is placed 20 mm in front of the VP and 40 mm above the HP. Draw its projections.

Q 3. A point is placed on the HP, 20 mm in front of the VP. Draw its projections.

Q 4. A point is placed on the VP, 30 mm above the HP. Draw its projections.

Q 5. A point is placed 40 mm from both the planes, draw its projections.

Q 6. Draw the projections of a line, AB 30 mm in length that is parallel to both the HP and the VP.

Q 7. Draw the projections of a line, AB 30 mm in length that is parallel to HP and perpendicular the VP.

Q 8. Draw the projections of a line, CD 40 mm in length that is parallel to VP and perpendicular to the HP.

Q 9. Draw the projections of a line, AB 30 mm whose on end A is in the HP and it is perpendicular to it (the HP).

Q 10. Draw the projections of a line, AB 30 mm whose on end A is in the VP and it is perpendicular to it (the VP).

Q 11. Draw the projections of a line AB, 30 mm in length that is inclined to the HP at 30 degrees and also inclined to the VP at 45 degrees.

Q 12. Draw the projections of a line CD, 40 mm in length that is inclined to the HP at 45 degrees and also inclined to the VP at 30 degrees.

Q 13. Draw the projections of a line AB, 30 mm in length that is inclined at 45 degrees to both the HP and the VP.

Q 14. Draw the projections of a line CD, 40 mm in length that is inclined at 30 degrees to both the HP and the VP.

Q 15. Draw the projections of a circle of radius 30 mm whose surface is parallel to the HP and its closest distance from the VP is 20 mm.

Q 16. Draw the projections of a circle of radius 30 mm whose surface is parallel to the HP and touching the VP.

Q 17. Draw the projections of a Square of side 30 mm whose surface is parallel to the HP and two of its sides perpendicular to the VP.

Q 18. Draw the projections of a Square of side 30 mm whose surface is parallel to the HP and all its  sides equally inclined with the VP.

Q 19. Draw the projections of a pentagon of side 30 mm whose surface is parallel to the HP and one of its side is parallel to the VP.

Q 20. Draw the projections of a pentagon of side 40 mm whose surface is parallel to the HP and 20 mm above it. It also has one of its sides perpendicular to the VP.

Q 21. Draw the projections of a hexagon of side 30 mm whose surface is parallel to the HP and two of its sides are parallel to the VP.

Q 22. Draw the projections of a hexagon of side 40 mm whose surface is parallel to the HP and 25 mm above it. It also has two of its sides perpendicular to the VP.

Q 23. Draw the projections of an equilateral triangle of side 30 mm whose surface is parallel to the VP and one side perpendicular to the HP.

Q 24. Draw the projections of a circle of radius 20 mm that lies in the HP and 20 mm away from the VP.

Q 25. Draw the projections of a pentagon of side 30 mm whose surface is parallel to the VP and one of its side parallel to the HP and away from it.

Q 26. Draw the projections of a hexagon of side 30 mm whose surface is parallel to the HP and two of its sides perpendicular to the VP.