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Wood - Physical Properties


Quiz Questions

1.Moisture content of wood is defined as the weight of water in wood expressed as a fraction, usually a percentage, of the weight of oven dry wood. Weight, shrinkage, strength, and other properties depend upon the moisture content of wood.
True
False
2. Two primary factors affecting the weight of wood products are: density of the basic wood structure and moisture content.
True
False
3.What does figure 3-4 illustrate about?

(Refer Pg. 3-11)
Typical moisture content-shrinkage curves
Variation in individual tangential shrinkage values of several Douglas-fir boards from one locality, dried from green condition
Tangential values for So
None of the above
4.Four important thermal properties of wood are thermal conductivity, heat capacity, thermal diffusivity, and coefficient of thermal expansion.
True
False
5.Thermal conductivity is a measure of the rate of heat flow through one unit thickness of a material subjected to a temperature gradient.
True
False
6.Moisture and temperature, which vary greatly with local conditions, are the principal factors that affect rate of decay.
True
False
7.Considerable difference in service life can be obtained from pieces of wood cut from the same species, even from the same tree, and used under apparently similar conditions.
True
False
8.Heat capacity is defined as the amount of energy needed to increase one unit of mass (kg or lb) one unit in temperature (K or F).
True
False

9.Wood exchanges moisture with air; the amount and direction of the exchange (gain or loss) depend on the relative humidity and temperature of the air and the current amount of water in the wood.
True
False
10.Grain is often used in reference to annual rings, as in fine grain and coarse grain, but it is also used to indicate the direction of fibers, as in straight grain, spiral grain, and curly grain.
True
False
11.The moisture content at which wood will sink in water (Msink) can be calculated by:
Wood - Physical Properties

What does Gb mean?

Basic specific gravity
Over dry weight
Grading
None of the above
12.Equilibrium moisture content (EMC) is defined as that moisture content at which the wood is neither gaining nor losing moisture; an equilibrium condition has been reached.
True
False
13.Oven dry weight and green volume are often used in databases to characterize specific gravity of species, which is referred to as basic specific gravity.
True
False
14.The major factors other than density that can affect production of smooth surfaces during wood machining are:
Interlocked and variable grain
Hard mineral deposits,
Reaction wood
All of the above
15.The thermal conductivity of wood is affected by a number of basic factors: density, moisture content, extractive content, grain direction, structural irregularities such as checks and knots, fibril angle, and temperature.
True
False
16.For moisture content levels below 25%, approximate thermal conductivity k across the grain can be calculated with a linear equation of the form

k = G (B + CM) + A
Where:
G is specific gravity based on oven dry weight and
A, B, and C are constants
M =?
What does M stand for?

Mass of the grain
Mean
Volume at a given moisture content(%)
None of the above
17.Diffusivity is defined as the ratio of conductivity to the product of heat capacity and density.
True
False
18.The coefficient of thermal expansion is a measure of the change of dimension caused by temperature change.
True
False
19.The electrical conductivity of wood (or its reciprocal, resistivity) varies greatly with moisture content, especially below the fiber saturation point.
True
False
20.When a nonconductor is placed in an electric field, it absorbs and stores potential energy. The amount of energy stored per unit volume depends upon the dielectric constant and the magnitude of the applied field.
True
False