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3 years ago

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Calculate the number of vacancies per cubic meter at 1000∘C for a metal that has an energy for vacancy formation of 1.22 eV/atom

, a density of 6.25g/cm^3, and an atomic weight of 37.4 g/mol.
(A) 1.49×10^18 m^−3
(B) 7.18×10^22 m^−3
(C) 1.49×10^24 m^−3
(D) 2.57×10^24 m^−3

1 answer:

Makovka662 [10]3 years ago

6 0

Answer:

C

Explanation:

N = Na.P/A------(1)

Na = avogadro's number = 6.02210²³

P = density

A = atomic weight of metal

When we substitute into equation 1 above we get

1.0x10²⁹atoms/m³

From here we calculate the number of vacancies

T = 1000⁰c = 1273K

The formula to use is

Nv= Nexo(Qt/K.T) -----(2)

Qt = 1.22eV

K = Boltzmann's constant = 8.6210x10^-5

When we substitute values into equation 2

We get Nv = 1.49 x 10²⁴m-3

Therefore option c is correct

Check attachment for a more detailed calculation of this question

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An aluminum alloy tube with an outside diameter of 3.50 in. and a wall thickness of 0.30 in. is used as a 14 ft long column. Ass

slega [8]

Answer:

slenderness ratio = 147.8

buckling load = 13.62 kips

Explanation:

Given data:

outside diameter is 3.50 inc

wall thickness 0.30 inc

length of column is 14 ft

E = 10,000 ksi

moment of inertia $= \frac{\pi}{64 (D_O^2 -D_i^2)}$

$I = \frac{\pi}{64}(3.5^2 -2.9^2) = 3.894 in^4$

Area $= \frac{\pi}{4} (3.5^2 -2.9^2) = 3.015 in^2$

$radius = \sqrt{\frac{I}{A}}$

$r = \sqrt{\frac{3.894}{3.015}$

r = 1.136 in

slenderness ratio $= \frac{L}{r}$

$= \frac{14 *12}{1.136} = 147.8$

buckling load $= P_cr = \frac{\pi^2 EI}}{l^2}$

$P_{cr} = \frac{\pi^2 *10,000*3.844}{( 14\times 12)^2}$

$P_{cr} = 13.62 kips$

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3 years ago

(D)<br> 13. Describe the differences between an impact socket and a conventional socket.

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Answer:

The wall of an impact socket is around 50% thicker than that of a regular socket, making it suitable for use with pneumatic impact tools, whereas regular sockets should only be used on hand tools.

Explanation:

This allows the socket to remain securely attached to the impact wrench anvil, even under high stress situations.

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2 years ago

A cylindrical resistor element on a circuit board dissipates 0.6 W of power. The resistor is 1.5 cm long, and has a diameter of

Burka [1]

Answer:

a. 51.84Kj

b. 2808.99 W/m^2

c. 11.75%

Explanation:

Amount of heat this resistor dissipates during a 24-hour period

= amount of power dissipated * time

= 0.6 * 24 = 14.4 Watt hour

(Note 3.6Watt hour = 1Kj )

=14.4*3.6 = 51.84Kj

Heat flux = amount of power dissipated/ surface area

surface area = area of the two circular end + area of the curve surface

$=2*\frac{\pi D^{2} }{4} + \pi DL\\=2*\frac{\pi *(\frac{0.4}{100} )^{2} }{4} + \pi *\frac{0.4}{100} *\frac{1.5}{100}$

= 2.136 *10^-4 $m^{2}$

Heat flux = $\frac{0.6}{2.136 * 10^{-4} }$ = 2808.99 $W/m^{2}$

fraction of heat dissipated from the top and bottom surface

$=\frac{\frac{2*\pi D^{2} }{4} }{\frac{2*\pi D^{2}}{4} + \pi DL } \\\\=\\\frac{\frac{2*\pi *(\frac{0.4}{100} )^{2} }{4} }{\frac{2*\pi *(\frac{0.4}{100} )^{2} }{4} +\pi *\frac{0.4}{100} *\frac{1.5}{100} } \\\\=\frac{2.51*10^{-5} }{2.136*10^{-4} } \\\\\= 0.1175$

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3 years ago

Read 2 more answers

Which of the following explains the purpose of a convertible screwdriver?

aliya0001 [1]

Answer:

The correct option is;

To be able to switch between different heads quickly and easily

Explanation:

A screwdriver is a tool or device that has a grip handle which surrounds an extension shaft that has a forged tip that fits into the complementary groove on a screw head such that by turning the handle while the forged head of the screwdriver sits in a screw head, the screw is turned

A convertible screw driver is built with the capability to easily change the tip or other attributes of the screwdriver quickly.

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2 years ago

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gulaghasi [49]

Answer:

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Explanation:

From the question we are told that:

Zener diode Voltage $V_z=9.1-V$

Zener diode Current $I_z=9 .A$

Note

$rz = 40\\\\IZK= 0.5 mA$

Supply Voltage $V_s=15$

Reduction Percentage $P_r= 50 \%$

Generally the equation for Kirchhoff's Voltage Law is mathematically given by

$V_z=V_{zo}+I_zr_z$

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$V_{zo}=8.74V$

Therefore

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$V_z=V_{z0}+I_zr_z$

$V_z=8.74+(10*10^{-3}) (40)$

$V_z=9.1v$

Generally the equation for Kirchhoff's Current Law is mathematically given by

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$I=10mA+\frac{9.1}{0}$

$I=10mA$

Therefore

$R=\frac{15V-V_z}{I}$

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$R=589 ohms$

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3 years ago