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Pachacha [2.7K]
3 years ago
15

A circular ceramic plate that can be modeled as a blackbody is being heated by an electrical heater. The plate is 30 cm in diame

ter and is situated in a surrounding ambient temperature of 15°C where the natural convection heat transfer coefficient is 12 W/m2·K. If the efficiency of the electrical heater to transfer heat to the plate is 80%, determine the electric power that the heater needs to keep the surface temperature of the plate at 220°C.
Engineering
1 answer:
denis23 [38]3 years ago
5 0

Answer:

Q = 125.538 W

Explanation:

Given data:

D = 30 cm

Temperature T_\infity = 15 degree celcius

T_S =  220 + 273 = 473 K

Heat coefficient = 12 W/m^2 K

Efficiency 80% = 0.8

Q = hA(T_S - T_{\infty}) \eta

= 12(\frac{\pi}{4} 0.3^2) (473 - 288) 0.8

Q = 125.538 W

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marta [7]

Answer:

(a) 3.185*10^{21} cells

(b) 6.37*10^{21} atoms

Explanation:

(a)

Volume, V of unit cell

V=(2.866*10^{-8})^{3}=2.354*10^{-23}

Number of unit cells, N

N=\frac {W_{mat}}{V\rho_{mat}} Where W_{mat} is weight of material and \rho_{mat} is density of material

N=\frac{0.59}{7.87*(2.354*10^{-23}}=3.185*10^{21} cells

(b)

Number of atoms in paper clip

This is a product of number of unit cells and number of atoms per cell

Since iron has 2 atoms per cell

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8 0
3 years ago
A centimeter is Viooth of a meter, while a kilo-
tatuchka [14]

Answer:

b. False

Explanation:

A centimeter is a hundredth of a meter. This means 1/100 ,1 cm = 0.01 m

A kilo is 1000 grams.

The first answer is false because a hundredth isnot written well.

The second statement is false because the comparison given is of different units of measure. For distance is meters where as for weight is kilograms.

8 0
3 years ago
A closed system of mass 10 kg undergoes a process during which there is energy transfer by work from the system of 0.147 kJ per
mr_godi [17]

Answer:

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Explanation:

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Δu= -5 kJ/kg

ΔKE + ΔPE+ ΔU= Q-W

0.5×m×(30^2- 15^2)+ mgΔh+mΔu= Q-W

Q= W+ 0.5×m×(30^2- 15^2) +mgΔh+mΔu

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= 1.47 +3.375-4.8450-50

Q=-50.005 KJ

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Answer:

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