The scale in which three successive dimensions can be measured at a time is called _____.
📐 Understanding Engineering Scales
In technical drawing and surveying, scales are essential for representing large objects or distances on paper in a proportional manner. The type of scale used depends on the required precision and the number of dimensions to be measured. A dimension can be a unit (like meters), a sub-unit (like decimeters), and a further sub-unit (like centimeters).
🔬 Detailed Analysis of the Options
B. diagonal scale
This is the correct answer. A diagonal scale is designed to read three different dimensions. It's an enhancement of the plain scale, which can only read two. By using the principle of similar triangles, a diagonal line is drawn to divide the smallest division of the plain scale into even smaller parts. This allows for measurements like meters, decimeters, and centimeters, or yards, feet, and inches, all from the same scale.
C. plain scale
This is incorrect. A plain scale is used to read only two successive dimensions, such as meters and decimeters, or feet and inches. It cannot provide the third level of precision that a diagonal scale offers.
A. chord scale
This is incorrect. A chord scale is not used for measuring linear dimensions. Its purpose is to measure or set out angles without using a protractor. It consists of a line of chords, where the length of the chord for a given angle is marked on the scale.
D. vernier scale
This is incorrect in this context. While a vernier scale provides very high accuracy, it is a separate auxiliary scale that works in conjunction with a main scale to measure a fractional part of the main scale's smallest division. It doesn't inherently measure three dimensions in the way a diagonal scale does; it refines a single dimension's measurement.
📊 Summary of Different Scales
| Feature | Plain Scale | Diagonal Scale | Chord Scale | Vernier Scale |
|---|---|---|---|---|
| Primary Use | Measuring lengths | Measuring lengths with high precision | Measuring or setting angles | Increasing the precision of a main scale |
| Dimensions Read | Two successive dimensions | Three successive dimensions | Reads angles, not linear dimensions | Reads fractional parts of a main scale division |
| Principle | Simple linear divisions | Principle of similar triangles | Uses pre-calculated chord lengths for angles | Compares a slightly different auxiliary scale to a main scale |
💡 Study Tips
- Plain = 2D: Think of a "plain" or simple ruler. It can measure units and one sub-unit (two dimensions).
- Diagonal = 3D: The "diagonal" lines are the key to unlocking the third, smaller dimension of measurement.
- Chord = Angle: Associate the word "chord" with circles and angles, not linear measurement.
- Vernier = Precision: A vernier scale is all about adding extra precision to an existing scale.