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Engineering Drawing Basics

Basic Science & Engineering · Measurement, Drawing & Mechanics

Useful for: Railway RRB

Overview

Engineering drawing communicates the shape and size of objects through standard views, lines, scales and dimensions.

Key points

India (BIS) follows first-angle projection.
Main views: front view (elevation), top view (plan) and side view.
Line types: continuous thick for visible edges, dashed for hidden edges, thin chain for centre lines.
Scale 1:2 is a reduction; 2:1 is an enlargement; 1:1 is full size.
Dimensions are given in millimetres unless stated.

Explanation

In first-angle projection the top view is drawn below the front view.
Section views show internal details using hatching.
Isometric drawing shows three faces at 120° axes.
Dimension lines are thin with arrowheads.

Step by step

Identify the concept, tool or rule involved.
Recall the definition, value or procedure.
Check units, safety logic and the direction of the effect.

Examples

On a 1:100 scale, 1 cm on paper represents 1 m.
Hidden edges are shown by dashed lines.
Centre lines are drawn as thin chain lines.

Traps and advanced points

Trap: Placing the top view above the front view in first-angle projection.
Trap: Using dashed lines for visible edges.
Trap: Reading 1:2 as enlargement.

Quick revision

First-angle (BIS).
Dashed = hidden; chain = centre.
1:n reduction.

Practice MCQs

Exam practice: The SI unit of electrical resistance is what?
1. ampere
2. tesla
3. ohm
4. coulomb
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Answer: (c) ohm. The SI unit of electrical resistance is ohm.
Exam practice: Vitamin B3 deficiency causes what?
1. Pellagra
2. Night blindness
3. Beriberi
4. Scurvy
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Answer: (a) Pellagra. Vitamin B3 deficiency causes Pellagra.
ALP Basic Science & Engineering: Complete the statement: “First-angle and third-angle projection are methods used in ____.”
1. protect a circuit from excessive current
2. engineering drawing
3. volatile working memory
4. watt
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Answer: (b) engineering drawing. First-angle and third-angle projection are methods used in engineering drawing. They define orthographic-view placement conventions.
ALP Basic Science & Engineering: Complete the statement: “An isometric drawing is mainly used to ____.”
1. P = VI
2. engineering drawing
3. represent a 3D object on a 2D surface
4. Personal Protective Equipment
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Answer: (c) represent a 3D object on a 2D surface. An isometric drawing is mainly used to represent a 3D object on a 2D surface. Three principal axes are shown with equal scale convention.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “engineering drawing”?
1. earthing primarily provides
2. first-angle and third-angle projection are methods used in
3. first aid for severe electrical shock begins with
4. greenhouse effect is intensified by increased atmospheric
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Answer: (b) first-angle and third-angle projection are methods used in. The correct answer is “first-angle and third-angle projection are methods used in”. They define orthographic-view placement conventions.
ALP Basic Science & Engineering: Which statement opening is correctly completed by “represent a 3D object on a 2D surface”?
1. a fuse is primarily used to
2. first-angle and third-angle projection are methods used in
3. SI base unit of length
4. an isometric drawing is mainly used to
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Answer: (d) an isometric drawing is mainly used to. The correct answer is “an isometric drawing is mainly used to”. Three principal axes are shown with equal scale convention.