Answer:
Feathers are great thermal insulators.
Explanation:
Feathers are great thermal insulators. The loose structure of down feathers traps air.
As a result, energy cannot be transmitted easily through down feathers. This means birds are insulated from cold air outside, plus their body heat doesn't escape easily either.
Human beings discovered that down feathers are good for insulation long ago. For example, documents from the 1600s show that Russian merchants sold “bird down" to the Dutch hundreds of years ago.
Today, down is used in all sorts of products, including coats, bedding, and sleeping bags, to help better insulate the user from cold weather. Down can be collected from many different types of birds, but most of today's supply comes from domestic geese.
If you have a down coat or comforter, is it all down? In the United States, laws require that products labeled “100 percent down" contain only down feathers.
If your product is labeled “down," it can contain a mixture of both down feathers and synthetic fibers. Not all down feathers are created equal, though.
Down insulation is rated on a measure called “fill power." The higher the fill power, the more the down insulates.
The highest fill-power rating — 1200 — goes to eiderdown, which comes from the Common Eider duck. Eiderdown tends to be expensive.
Explanation:
→ Volume of cone = πr² × h/3
Here,
- Radius (r) = 13 cm
- Height (h) = 27 cm
→ Volume of cone = π(13)² × 27/3 cm³
→ Volume of cone = 169π × 9 cm³
→ Volume of cone = 1521π cm³
→ Volume of cone = 1521 × 22/7 cm³
→ Volume of cone = 33462/7 cm³
→ <u>Volume of cone = 4780.28 cm³</u>
Answer:
We have a not significant increase of the population until 1700s or 1800s and then a significant increase growth from these years to the present.
Explanation:
From the figure attached we see the evolution of the human population since early times (1050).
We see that from 1050 until 1750-1850 we have an increase slowly with a low value for the increase per year.
But after these years (1750-1850) we see a considerable increase of the population, like an exponential model.
So then we can conclude in general terms this:
We have a not significant increase of the population until 1700s or 1800s and then a significant increase growth from these years to the present.
Answer: Idk I think I forgot
Explanation:
To find the electron and hole concentrations and fermi levels in silicon at 300 k for boron, fermi level is 9.3 x
.
<h3>Calculation and Explanation</h3>
Ionization energy for boron in Si, 0.045 eV
Fermi level in silicon,
300 K at
(Boron atoms)
All boron impurities are ionized, 300K
Electron, hole concentrations and Fermi levels is found out,
The value of Na = 
np = 
np = 
np= 9.3 x 
Fermi level is calculated,
Ef - Ev = kT ln(NV/ND)
value of kT = 0.0259 eV (300° K)
So, substitution the values
Ef - Ev = kT ln(NV/ND)
Ef - Ev = 0.0259ln (2.66 x
)
Ef - Ev = 0.0259ln (26600)
Ef - Ev = 0.0259 x 10.18
Ef - Ev = 0.263 eV
What is ionization energy?
Ionization energy, also known as ionization energy (IE) or ionization energy (British English spelling), is the minimal amount of energy needed to free the most loosely bonded electron from an isolated gaseous atom, positive ion, or molecule in physics and chemistry.
To know more about ionization energy, visit:
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