Nêu đặc điểm của tín hiệu PAM rời rạc dạng lưỡng cực NRZ, RZ

What do electrons have to do with electrical current?

erastova [34]

Answer:

Electrons in atoms can act as our charge carrier, because every electron carries a negative charge. If we can free an electron from an atom and force it to move, we can create electricity.

6 0

4 years ago

Ground effect is felt at a height that is equal to the plane's wingspan.<br> True or False

Oliga [24]

Answer:

True

Explanation:

7 0

3 years ago

A solid shaft and a hollow shaft of the same material have same length and outer radius R. The inner radius of the hollow shaft

alexandr402 [8]

Answer with Explanation:

By the equation or Torque we have

$\frac{T}{I_{p}}=\frac{\tau }{r}=\frac{G\theta }{L}$

where

T is the torque applied on the shaft

$I_{p}$ is the polar moment of inertia of the shaft

$\tau$ is the shear stress developed at a distance 'r' from the center of the shaft

$\theta$ is the angle of twist of the shaft

'G' is the modulus of rigidity of the shaft

We know that for solid shaft $I_{p}=\frac{\pi R^4}{2}$

For a hollow shaft $I_{p}=\frac{\pi (R_o^4-R_i^4)}{2}$

Since the two shafts are subjected to same torque from the relation of Torque we have

1) For solid shaft

$\frac{2T}{\pi R^4}\times r=\tau _{solid}$

2) For hollow shaft we have

$\tau _{hollow}=\frac{2T}{\pi (R^4-0.7R^4)}\times r=\frac{2T}{\pi 0.76R^4}$

Comparing the above 2 relations we see

$\frac{\tau _{solid}}{\tau _{hollow}}=0.76$

Similarly for angle of twist we can see

$\frac{\theta _{solid}}{\theta _{hollow}}=\frac{\frac{LT}{I_{solid}}}{\frac{LT}{I_{hollow}}}=\frac{I_{hollow}}{I_{solid}}=1.316$

Part b)

Strength of solid shaft = $\tau _{max}=\frac{T\times R}{I_{solid}}$

Weight of solid shaft = $\rho \times \pi R^2\times L$

Strength per unit weight of solid shaft = $\frac{\tau _{max}}{W}=\frac{T\times R}{I_{solid}}\times \frac{1}{\rho \times \pi R^2\times L}=\frac{2T}{\rho \pi ^2R^5L}$

Strength of hollow shaft = $\tau '_{max}=\frac{T\times R}{I_{hollow}}$

Weight of hollow shaft = $\rho \times \pi (R^2-0.7R^2)\times L$

Strength per unit weight of hollow shaft = $\frac{\tau _{max}}{W}=\frac{T\times R}{I_{hollow}}\times \frac{1}{\rho \times \pi (R^2-0.7^2)\times L}=\frac{5.16T}{\rho \pi ^2R^5L}$

Thus $\frac{Strength/Weight _{hollow}}{Strength/Weight _{Solid}}=5.16$

3 0

3 years ago

If copper (which has a melting point of 1085°C) homogeneously nucleates at 849°C, calculate the critical radius given values of

____ [38]

Answer:

The critical radius is -1.30 nm

Explanation:

Temperature for homogenous nucleation of copper, $T_{H} = 849^{0} C = 849 + 273 = 1122 K$

Melting point of copper, $T_{cu} = 1085^{0} C = 1085 + 273 = 1358 K$

Latent heat of fusion, $H_{f} = -1.77 * 10^{9} J/m^{3}$

Surface free energy, $\gamma = 0.200 J/m^{2}$

Critical radius, r = ?

The formula for the critical radius is given by:

$r = \frac{2 \gamma T_{cu} }{H_{f}(T_{cu} - T_{H}) }$

$r = \frac{2 * 0.2*1358 }{(-1.77 * 10^{9}) (1358 - 1122) }$

$r = \frac{543.2 }{(-1.77 * 10^{9}) 236}\\r = -1.30 * 10^{-9} m\\r = -1.30 nm$

The critical radius is -1.30 nm

8 0

4 years ago

Read Shakespeare's "Sonnet 100.”

liraira [26]

Answer: quatrain

Explanation:

Reading the Shakespeare's "Sonnet 100", we can infer that the underlined section is referred to as a quatrain.

The quatrain simply refers to a type of stanza that is made up of four lines. For example, based on the information given, we can deduce that the rhyme scheme for the second quatrain is given as cdcd.

7 0

3 years ago