SSC-JUNIOR ENGINEER (Civil & Structural) Online Exam 2016

Paper-I

Total Questions: 50

21. Closed contours with higher value inside represents a _________.

Correct Answer: B. hill
Solution:An imaginary line, on the ground, joining the points of equal elevation above the assumed datum is called a contour. Survey work, including office work in the preparation of a contour plan is known as contouring.

The vertical distance between any two conse-cutive contours is called contour interval.

The least horizontal distance between two consecutive contours is called horizontal equivalent.

Characteristics of Contours: The characteristics of contour given below are useful in plotting and for interpreting a contour map correctly.

1. Contour which is equally spaced represents a uniform slope whereas one which is closely spaced represents a steep slope.

2. A series of straight, parallel, equally spaced contours represents an inclined plane surface.

3. Contour at any point is perpendicular to the line of the steepest slope at that point.

4. A series of closed contours with higher values on the inside, represents a hill and lower value on the inside indicates a pond or depression without an outlet as shown in in figure.

22. In a theodolite the line of collimation is __________.

Correct Answer: C. Perpendicular to the trunnion axis
Solution:General construction of the theodolite

There are certain fundamental relationships and components which are common to all theodolites. Before examining the detailed construction of a modern glass arc theodolite, it is important to appreciate the geometrical arrangement of the axes of a theodolite, as illustrated in the figure.

In this ideal arrangement the vertical axis is vertical, the trunnion axis is perpendicular to it and hence horizontal, and the line of collimation is perpendicular to the trunnion axis.

23. How is the size of the theodolite specified?

Correct Answer: D. By the diameter of lower plate
Solution:Size of a Theodolite is specified by the diameter of the lower plate. If the lower clamp screw is tightened and upper clamp screw is loosened, the Theodolite may be rotated on its inner spindle with a relative motion between the vernier and the graduated scale of lower plate.

24. In the surveys, the slope correction applied to the base line is _________.

Correct Answer: A. Always cumulative
Solution:No explanation given in the book

25. Contour interval on map sheet denotes _________.

Correct Answer: B. Vertical distance between two successive Contour lines
Solution:Contour or contour lines: "A contour is an imaginary line of constant elevation on the surface of the ground". Contours are represented on the map by contour lines. The contour and contour lines are often used interchangeably.

Contour interval: "The vertical distance between any two successive contours on a given map is called the contour interval". Contour intervals usually vary from 25 to 250 cm in engineering work. In rough country, the vertical distance between contours is kept greater while in flat areas 25 to 50 cm contour intervals are used.

26. Which of the following is the correct meaning of the term 'level line' in surveying?

Correct Answer: A. The line parallel to the mean spheroidal surface of earth.
Solution:Level Line: Any portion of the line lying on the great circle of the earth is called a level line. It may also be defined as a line lying on the level surface and normal to the plumb line at all the points.

27. The type of surveying in which the curvature of the earth is taken into account is called _________.

Correct Answer: A. Geodetic surveying
Solution:Geodetic Surveying

Geodetic surveying is that type of surveying where the curvature of earth is considered. It is essential if the area of survey is quite large. Actual curvature of the earth is taken into account in this type of survey. The lines on the earth surface are curved; and triangles are spherical.

It, therefore, invites spherical trigonometry. Science of geodesy is required in this type of survey. The main object of geodetic surveying is to determine the precise location of widely spaced on the surface of the earth.

28. The method of levelling used to carry out reconnaissance of area is:

Correct Answer: B. Fly levelling
Solution:Fly Levelling: Fly levelling involves taking levels continuously from a point of known reduced level to a forward point of unknown level, with a number of changes in the level positions. Readings may also be taken from one or more of the level stations to other points of interest along the route. Distances between points, or between staff stations and level positions, are not of interest in this kind of work; the reduced levels of certain points are of specific interest.

The fieldwork involved is as follows: The level is set up at the first station in such a way that the first point of known level is within sighting range of the instrument.

The reading of the staff held at the first point is taken, after the temporary adjustments have been made. The telescope is rotated to the forward direction, the staffman directed to keep the staff at a convenient point ahead to cover a fair distance, and the reading taken.

Then the instrument is shifted to a point-ahead of the staff in the forward direction and a reading taken on the previous staff position after carrying out the temporary adjustments.

The process is repeated at a sufficient number of instrument positions until the point whose reduced level is sought is reached.

29. In a closed traverse _________.

Correct Answer: B. sum of included angles should be (2N - 4) times right angle, where N represents the number of sides
Solution:Traversing is that type of survey in which a number of connected survey lines form the framework and the directions and lengths of the survey lines are measured with the help of an angle measuring instrument and a tape or chain respectively.

Types of Surveying: There are two types of traverse surveying. They are:

1. Closed traverse: When the lines form a circuit which ends at the starting point, it is known as closed traverse.

2. Open traverse: When the lines form a circuit which ends elsewhere except starting point, it is said to be an open traverse.

In interior angle adjustment method, the algebraic sum of the interior angles is being computed and needs to be (2n - 4) × 90°, where n is the number of sides in the traverse. If there is no difference, no error is associated with the observation. Otherwise there is an error in observation of interior angles.

The amount of error is distributed equally among all the interior angles to find their corrected values. Then, azimuth of the line is computed using the adjusted interior angles.

30. The Horizontal angle which the true meridian makes with magnetic meridian is called __________.

Correct Answer: A. Magnetic declination
Solution:The magnetic azimuth or bearing of a line can be determined by direct reading of a compass. Converting magnetic readings to true readings by applying the magnetic declination for the location can approximate the true azimuth or bearing in question.

Many compasses used by foresters have the capability of being adjusted for declination. The magnetic declination is the angle between the true meridian and the magnetic meridian.