Index Properties MCQ with answer and solution

Concept

Equivalent moisture (or moisture equivalent) is the amount of water a soil can hold against a very high centrifugal force.

Step-by-step solution

1. Moisture equivalent is a laboratory test used to understand how soil holds water. 2. In this test, a saturated soil sample is placed in a centrifuge machine. 3. The machine rotates the soil at a very high speed to create a centrifugal force. 4. Standard practice defines this force as 1000 times the force of gravity (1000g). 5. The water that remains in the soil after this process is measured as a percentage of dry weight. Answer: (C) 1000

Explanation

Moisture equivalent helps classify soils based on their water-holding capacity. A centrifugal force of 1000 times gravity is used to remove 'free' water, leaving only the water held tightly by soil particles. This value is particularly useful for identifying fine-grained soils like silts and clays.

Why the other options are wrong

A: 10 is too low to overcome the capillary forces in fine soils. B: 100 is not the standard value used in the moisture equivalent test. D: 10000 is an extremely high force not required for this standard soil test.

Shortcut

Remember 'M' for Moisture and '1000' (M is the Roman numeral for 1000).

Common mistake

Students often confuse this with 'Field Capacity' which is related to gravity alone, not a centrifuge.