Introduction

Are you preparing for the NEC License Exam and looking for authentic collections of past questions? Here are 10 important, solved old questions taken from previous NEC exams. These questions will help you get familiar with the real exam pattern, increase your accuracy, and enhance your confidence.

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10 MCQs from Past paper

1) Early strength of cement is achieved by [Old Question]

a) $C_{3} S$

b) $C_{2} S$

c) $C_{3} A$

d) $C_{4} A F$

correct answer: option (a) $C_{3} S$

Explanations:

Tricalcium silicate ( $C_{3} S$ ) is primarily responsible for the early strength (first 7 days) of cement due to its faster hydration and higher early heat evolution.

Dicalcium silicate ( $C_{2} S$ ) contributes more to later strength, while $C_{3} A$ and $C_{4} A F$ have lesser roles in strength development compared to $C_{3} S$ .

2) Le-Chatelier’s device is used for determining the: [Old Question]

a) Setting time of cement

b) Tensile Strength

c) Soundness

d) Compressive strength

correct answer: option (c) Soundness

Explanations:

Le-Chatelier’s apparatus is used to determine the soundness of cement, which assesses its stability in volume after setting—primarily to check for excess free lime or magnesia that can cause delayed expansion.

Other options:

a) Setting time is measured using the Vicat apparatus.

b) Tensile strength is tested using briquette specimens in a tensile testing machine.

d) Compressive strength is tested by crushing cube or cylinder specimens in a compression testing machine.

3) Terracotta is used in buildings for [Old Question]

a) Ornamental work

b) Insulation

c) Storage

d) None

correct answer : option (a) ornamental work

Explanation:

Terracotta (fired clay) is widely used for architectural ornaments, facades, cornices, tiles, jalis, and decorative elements due to its moldability and aesthetic finish.

While terracotta does have some insulating properties (option b), its primary use in construction is for decorative and ornamental purposes. It is not typically used for storage (option c) in the context of building materials.

4) The bench marks are fixed during the [Old Question]

a) Preliminary survey

b) Detailed survey

c) Reconnaissance

d) After detailed project report

correct answer: option(b) Detailed survey

Explanation:

Bench marks (permanent reference points with known elevation) are ordinarily established during the detailed survey, when precise vertical control is required and is tied densely to the project layout.

Reconnaissance: This is a visual, walk-through inspection. No precise measurements are taken, and no permanent marks are established.
Preliminary Survey: This survey establishes a basic control network. While some temporary benchmarks may be used for initial planning and cost estimation, the marks are not typically intended to be permanent or to the high precision required for construction.

5) How much minimum depth below soil, footing is provided? [Old Question]

a) 400 mm

b) 500 mm

c) 600 mm

d) 300 mm

correct answer: option(b) 500mm

Explanation:

As per IS:1904, foundations must extend at least 50 cm (500 mm) below natural ground level to ensure stability and protect against surface changes like erosion or moisture variations. This applies generally to residential buildings, though actual depths may vary by soil type

6) A non-Newtonian fluid is one which [Old Question]

a) Doesn’t follow Newton’s law of viscosity

b) Is a mathematical concept

c) Follow that shear stress is directly proportional to velocity gradient

d) Has properties of real fluid

correct answer: option (a) Doesn’t follow Newton’s law of viscosity

Explanation:

A Newtonian fluid (e.g., water, air) follows Newton's law of viscosity, which states that the shear stress (τ) is directly proportional to the velocity gradient (du/dy) in the direction of flow. (e.g., water, alcohol etc.). The constant of proportionality is the dynamic viscosity (μ):

$τ = μ \frac{d u}{d y}$

A non-Newtonian fluid does not obey this linear relationship. Its viscosity may change with the applied shear stress or shear rate (e.g., ketchup, blood, paint)

7) Momentum principle is not applicable to [Old Question]

a) Force on plate

b) Force on bend

c) Venturi meter

d) Force in moving plate

correct answer: option (c) Venturi meter

Explanations:

The momentum principle is not applicable to a Venturi meter because it operates based on the Bernoulli's principle rather than momentum analysis.

The momentum principle calculates forces from changes in fluid momentum, such as for impacts on plates (stationary or moving) or bends in pipes. However, a venturi meter measures flow rate using Bernoulli's principle (energy conservation) and continuity, not momentum.

8) Prandtl mixing length is [Old Question]

a) A universal constant

b) Zero at the pipe wall

c) Independent of shear stress

d) Independent of radial distance from pipe axis

correct answer: option(b) Zero at the pipe wall

Explanation:

The Prandtl mixing length is zero at the pipe wall due to the fundamental physics of turbulent flow near solid boundaries.

The mixing length (l) represents the average distance that a fluid particle travels in the transverse direction before exchanging its momentum with surrounding fluid particles. It's conceptually similar to the mean free path in kinetic theory of gases.

In pipe flow, Prandtl assumed that the mixing length varies linearly with distance from the wall:

l = ky

Where:

k = Kármán constant ≈ 0.4
y = distance from the pipe wall

9) Precipitation caused by lifting of an air mass due to the pressure difference, is called [Old Question]

a) Cyclonic precipitation

b) Convective precipitation

c) Orographic precipitation

d) None of these

correct answer: options(a) Cyclonic precipitation

Explanation:

Precipitation caused by the lifting of an air mass due to pressure difference is called cyclonic precipitation.

Definition: Cyclonic precipitation is caused by the movement of moist air masses into regions of low atmospheric pressure, where the pressure difference forces the air to rise, cool, and condense

Mechanism: A cyclone is a large low-pressure region with circular wind motion. The pressure gradient forces air masses to move toward the low-pressure center, causing them to rise and form precipitation.

Other options:

b) Convective precipitation

Caused by temperature differences, not pressure differences
Results from localized heating causing warmer air to rise

c) Orographic precipitation

Caused by topographic barriers like mountains
Air masses are forced upward by physical obstacles, not pressure differences

10) The locus of reaction of a two hinged semi-circular arch is [Old Question]

a) Straight Line

b) Parabola

c) Circle

d) Hyperbola

correct answer: option(a) Straight Line

Explanation:

For a two-hinged semi-circular arch, the reaction locus is a straight line parallel to the line joining the abutments with a height at πR/2 (where R is the radius).

This occurs due to:

Symmetric nature of the semi-circular arch
Linear relationship between horizontal and vertical reaction components
Geometric properties of the circular arch shape

Comparison with Other Arch Types:

Semi-circular arch: Locus = Straight line

Parabolic arch: Locus = Parabolic curve

Conclusion

These 10 past NEC License Exam questions with detailed solutions will give you a realistic idea of the actual exam pattern and help you enhance your accuracy and confidence. There is no better way to study for the NEC license exam than regular practice with past papers and mock tests.

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