Bulk modulus is the ratio bulk stress to the bulk strain.Bulk stress is the force acting on a body per unit area in all directions.Generally this is also referred as pressure.Bulk strain is the ratio of change in the volume to its original volume.
When a body is submerged in a fluid, it undergoes a hydraulic stress (equal in magnitude to the hydraulic pressure). This leads to the decrease in the volume of the body thus producing a strain called volume strain . The ratio of hydraulic stress to the corresponding hydraulic strain is called bulk modulus. It is denoted by symbol B.
B = – p/(ΔV/V)
The negative sign indicates the fact that with an increase in pressure, a decrease in volume occurs. That is, if p is positive, ΔV is negative.Thus for a system in equilibrium, the value of bulk modulus B is always positive. SI unit of bulk modulus is the same as that of pressure i.e., N m–2 or Pa.
The reciprocal of the bulk modulus is called compressibility and is denoted by k. It is defined as the fractional change in volume per unit increase in pressure.
k = (1/B) = – (1/Δp) × (ΔV/V)
Bulk moduli for solids are much larger than for liquids, which are again much larger than the bulk modulus for gases (air).
Thus solids are least compressible whereas gases are most compressible. Gases are about a million times more compressible than solids! Gases have large compressibility, which vary with pressure and temperature.
The in compressibility of the solids is primarily due to the tight coupling between the neighboring atoms. The molecules in liquids are also bound with their neighbors but not as strong as in solids. Molecules in gases are very poorly coupled to their neighbors.
Related posts :
Shear modulus
Elastic behavior of Solids
Stress and strain
Stress and Strain Curve
Determination of Young's modules
When a body is submerged in a fluid, it undergoes a hydraulic stress (equal in magnitude to the hydraulic pressure). This leads to the decrease in the volume of the body thus producing a strain called volume strain . The ratio of hydraulic stress to the corresponding hydraulic strain is called bulk modulus. It is denoted by symbol B.
B = – p/(ΔV/V)
The negative sign indicates the fact that with an increase in pressure, a decrease in volume occurs. That is, if p is positive, ΔV is negative.Thus for a system in equilibrium, the value of bulk modulus B is always positive. SI unit of bulk modulus is the same as that of pressure i.e., N m–2 or Pa.
The reciprocal of the bulk modulus is called compressibility and is denoted by k. It is defined as the fractional change in volume per unit increase in pressure.
k = (1/B) = – (1/Δp) × (ΔV/V)
Bulk moduli for solids are much larger than for liquids, which are again much larger than the bulk modulus for gases (air).
Thus solids are least compressible whereas gases are most compressible. Gases are about a million times more compressible than solids! Gases have large compressibility, which vary with pressure and temperature.
The in compressibility of the solids is primarily due to the tight coupling between the neighboring atoms. The molecules in liquids are also bound with their neighbors but not as strong as in solids. Molecules in gases are very poorly coupled to their neighbors.
Related posts :
Elastic behavior of Solids
Stress and strain
Stress and Strain Curve
Determination of Young's modules
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