# physics

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1. Calculate the de Broglie wavelength in picometers (1 picometer =10^−12 meters) of an electron that has kinetic energy of 10 keV. The mass of an electron is 9.11 x 10^−31 kg

2. Winter is coming, so I want to make a 1500 W heating coil which will plug into a 120 V wall outlet. The coil will have a cross sectional area of 0.01 cm^2 and a length (when fully unwound) of 5 m.

Determine the resistivity of the coil required, in Ωcm:

3. At 300 K we see the electron concentration in the conduction band for pure (undoped) Si is 10^10/cm^3. How many electrons per Si atom is this? You can use scientific notation, as in A.AAeB

Si is diamond cubic with 8 Si atoms per unit cell and a lattice parameter of 0.543 nm.

• physics -

help me with plzzz
Water is a(n) __________ factor in all ecosystems that all living things require.

• physics -

important?

• physics -

KE=10⁴•1.6•10⁻¹⁹ =1.6•10 ⁻¹⁵J
KE=mv²/2 =m²v²/2m =p²/2m =>
p=sqrt(2m•KE)
λ=h/p =h/sqrt((2m•KE)=
=6.63•10⁻³⁴/sqrt(2•9.1•10 ⁻³¹•1.6•10 ⁻¹⁵)=
=1.22•10⁻¹¹ m=0.122 pm
-------
R=ρL/A
P= U²/R= U²A/ ρL
ρ= U²A/ PL =
=120²•10⁻²/1500•500=1.92•10⁻⁴Ω•cm

• physics -

0.122 is wrong......is that the full answer? are you missing something? the computer says it is wrong.

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