# A cube that is 20 nanometer on an edge contains 399,500 silicon atoms, and each silicon atom has 14 electrons and 14 protons. In the silicon we replace 4 silicon atoms with phosphorus atoms (15 electrons and 15 protons/atom), and we replace 7 silicon atoms with boron atoms (5 electrons and 5 protons/atom). How many "holes" are available to carry current at 300K? Holes look like positive mobile carriers. Three significant digits and fixed point notation.

Total 3 holes are available for conduction of current at 300K.

Explanation:

In order to develop a semiconductor, two type of impurities can be added as given below:

1. N-type Impurities: Pentavalent impurities e.g. Phosphorous, Arsenic are added to have an additional electron in the structure. Thus a pentavalent impurity creates 1 additional electron.
2. P-type Impurities: Trivalent impurities e.g. Boron, Aluminium are added to have a positive "hole" in the structure. Thus a trivalent impurity creates 1 hole.

Now for estimation of extra electrons in the impured structure is as

Now for estimation of "holes"  in the impured structure is as

Now when the free electrons and "holes" are available in the structure ,the "holes" will be filled by the free electrons therefore

So total 3 "holes" are available for conduction of current at 300K.

## Related Questions

How many prtons neutrons electrons are in helium

There are a truly huge, enormous number of all of them in
any sample of helium, no matter how small the sample is.

In just ONE ATOM of helium, there are 2 protons and 2 neutrons
inside the nucleus, and two electrons in the 'cloud' of probability
outside the nucleus.

Let the force of the Moon on the Earth be F1. Let the force of the Earth pulling on the Moon be F2. Which of the following is greater? F1 ⊝ F2 ⊝ neither F1 nor F2 ⊝ cannot be determined without additional information

The two forces are equal in magnitude but opposite in direction.

The given parameters:

• force of the moon on the Earth, = F1
• force of the Earth on the moon, = F2

According to Newton's third law of motion, action and reaction are equal and opposite.

F₁ = -F₂

The force exerted on the moon by the Earth, is equal in magnitude to the force exerted on the Earth by the moon but the forces are opposite in direction.

Thus, we can conclude that the two forces are equal in magnitude but opposite in direction.

I guess the answer is f2

If you hit the brakes of your bicycle does it still mean you’re accelerating

you will be decelerating

Explanation:

YOU ARE DECCELERATING

If it had been thrown with twice the speed in the same direction, it would have hit the ground in If it had been thrown with twice the speed in the same direction, it would have hit the ground in 3.20 s.
1.60 s.
0.800 s.
0.400 s.
0.200 s.

The ball will reach the ground in 0.8s

Option C

Explanation:

Given:

- Takes t = 0.8 s for ball to reach ground when thrown horizontal from top of a building.

Find:

If it had been thrown with twice the speed in the same direction, it would have hit the ground in how many second.

Solution:

- We know that the amount of time taken to hit the ground is determined by the vertical distance i.e height at which it is thrown. The displacement of ball from top is given by:

S_y = S_o + V_i,y*t + 0.5*g*t^2

- We know that the S_o = height of the building.

We also know that the ball os thrown horizontally; hence, y-component of initial velocity is zero. V_y,i = 0

0 = h + 0 + 0.5*g*t^2

- Hence, the time taken t is:

t = sqrt ( 2h / g)

- The time taken to reach the ground is independent of the initial speed. Hence, the ball will reach the ground in 0.8s .

What force is required to accelerate a block of mass 4 kg at 2m/s2 on a surface which has a frictional force of 2N.

Compare and contrast the properties of the terrestrial planets and the Jovian planets.

Explanation:

Planets in our  solar system are classified as terrestrial and Jovian.

• Terrestrial planets have solid surfaces while Jovian have gaseous surfaces.
• Mercury, Venus, Earth, Mars are the terrestrial planets and Jupiter, Saturn, Uranus, Neptune are Jovian planets.
• Nitrogen and carbon dioxide are abundant in the atmosphere of terrestrial planets while Jovian planets are rich in hydrogen and helium.
• Terrestrial planets have dense metallic core while Jovian planets have less  core, supposedly molten rock.

What is the net force on a 2 kg skateboard acceleration at a rate of 2 m/s2

Using the equasion F=ma F=2*2 F= 4N 4 Newtons or kg * m over s^2, the answer would be  12 m/s^2.

A periodic wave has a fixed pattern that is repeated. What is one completion of the wave pattern called?

A periodic wave has a fixed pattern that is repeated. One completion of the wave pattern is called as cycle of the wave.

Explanation:

Periodic waves are those which repeat the same kind of behaviour or pattern after a particular interval of time. So, completion of behaviour or pattern for a given time interval is termed as the cycle of wave.

Generally, one complete wave pattern makes a time interval of 2π. So each cycle will take nearly 2π time to form. The repetition of cycle in a time interval will help us to derive the frequency of the system.

How many Earth radii above the Earth (not from its center) must you be located to experience an acceleration of gravity of 1.38 m/s/s. Express in terms of Earth-radii; that is, express the answer as the number of times greater than 6.38 x 106 m. Ratio of altitude/REarth

It is necessary to be at 2.66 Earth radii to experience an acceleration of  .

Explanation:

The height above the earth surface necessary to experience an acceleration of can be found by means of the Universal law of gravity:

(1)

Then, replacing Newton's second law in equation 3 it is gotten:

(2)

Then, r can be isolated from equation 2

(3)

Where G is the gravitational constant, M is the mass of the Earth and a is the acceleration.

Hence, it is necessary to be at 2.66 Earth radii to experience an acceleration of  .