What is the ultimate source of energies for fossil fuels, solar cells and windmills?

1 answer:

7 0

The ultimate source of energies for fossil fuels, solar cells and windmills is the solar energy.
The sun is the ultimate source of energy for our planet. It is an alternative energy resource that cause no pollution and is <span>environment friendly. </span>

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Determine the frequency of light whose wavelength is 4.257 x 10-7 cm

marin [14]

$v = f (wavelength)$ i don't know what symbol ya'll use for wavelength so i just put the word instead.We use the greek symbol lambda.So just plug in everything you know.
wavelength=4.257×10^-7x10^-2 and
v=speed of light = 3×10^8
So you should get f= 7.04 ×10^15Hz

7 0

3 years ago

5. A stream of air at 12 bar and 900 K is mixed with another stream of air at 2 bar and 400 K with 2 times the mass flowrate. If

Softa [21]

Answer:

The anserrs to the question are

(a) The temperature would be 566.67 K and

(b) The pressure of the resulting air stream is 14 bar

Explanation:

Here the two streams of gases meet ad form a single stream

The steady-flow energy equation can be implemented at the mixing point of the to streams as follows

mₐhₐ₁ + mₙ hₙ₁ + Q° + W° = mₐhₐ₂ + mₙhₙ₂

Where the flow is adiabatic, we have

Q = 0 and W = 0 hence

mₐhₐ₁ + mₙ hₙ₁ = mₐhₐ₂ + mₙhₙ₂ where h = cp×T we have

mₐcpₐ×Tₐ + mₙcpₙ×Tₙ = mₐcpₐ×T + mₐcpₙ×T

Therefore the final temperature T is given by

$T = \frac{m_ac_{pa}T_a + m_nc_{pn}T_n}{m_ac_{pa} + m_nc_{pn}}$ for the same kind of gas cpₐ =cpₙ therefore

$T = \frac{m_aT_a + m_nT_n}{m_a + m_n}$ where mₐ and mₙ are mass flow rate

Therefore we have where Tₐ = = 900 K and Tₙ = 400 K and mₙ = 2mₐ gives

$T = \frac{m_a*900 + 2*m_a*400}{m_a + 2*m_a}$ = $T = \frac{900 + 800}{1 + 2}$ = 1700/3 = 566.67 K

From Dalton's law, the total pressure of a mixture of gases is equal to the sum of the partial pressures of the components of the mixture

Therefore the total pressure of the combined stream = pₐ + pₙ = p

= 12 bar + 2 bar = 14 bar

Stream pressure = 14 bar

4 0

3 years ago

A carnot heat engine receives 600 kj of heat from a source of unknown temperature and rejects 175 kj of it to a sink at 20°c. de

oee [108]

(b) 71%

The thermal efficiency of a Carnot heat engine is given by:

$\eta = \frac{W}{Q_{in}}$

where

W is the useful work done by the engine

$Q_{in}$ is the heat in input to the machine

In this problem, we have:

$Q_{in}=600 kJ$ is the heat absorbed

$W=600 kJ-175 kJ=425 kJ$ is the work done (175 kJ is the heat released to the sink, therefore the work done is equal to the difference between the heat in input and the heat released)