Category: Physics

P and N-type semiconductors

P and N-type semiconductors

N-type semiconductors

02/02/17

“What are the fundamentals of the fundamentals of solar cells?”
Solar cells are one of the most magnificent devices that humanity has conjured. However, what exactly makes them tick? To find out, let’s go take a look. If one were to analyze a solar cell with a magnifying glass so powerful that it could see in the microscopic level then we would find a multitude of small, three terminal devices. These devices are known as Transistors and have very special properties. Specifically, it can work as a switch without moving parts! However, before we understand transistors, we must understand what cause them to work. Half of the composition of transistors are composed of objects known as P-type and N-type semiconductors. P-type semiconductors hold an impurity of boron[B], which holds one less electron than silicon, while N-type semiconductors are  have a small impurity of phosphorous [P], which holds an extra electron than silicon. When combined, these semiconductors will have more mobile charges and can conduct current better.

Spherical Sun Power Generators

Spherical Sun Power Generators

Spherical Sun Power Generators

“Is the only thing we need for the next solar power revolution  just a simple change of geometry?”
The current design of solar panels have a distinct bottleneck; their rectangular geometry leaves them inefficient for obtaining solar power from the sun since the sun’s rays will be in a sub-optimal direction for most of the time. Solar trackers can also be inefficient and are prone to damage in the rain, so how can we completely transform the way we collect solar power? Well, let’s use our engineering mindset to figure this out. Our goal is to make the design of our solar producing unit so that the sun can be in an optimal angle at all times. If we think back to our geometry class, then we will remember that a sphere is symmetric from all directions. With this knowledge, the German architect Andre Broessel created a Spherical Sun Power Generator. The setup works as follows: A supporting structure will house a spherical lens. This spherical lens will have a dual tracking system structure at the back of it. In this tracking system will be solar cells, which will receive ample sunlight as a result of the focusing effect from the spherical lens. These spherical sun power generators allow for twice the conventional yield in a much smaller surface area, allowing it to even absorb the reflected sun light from the moon!

Internal energy

Internal energy

Internal energy

12/08/16

“How can we quantify the energy of internal molecules in a system?”

 

There seems to be a problem. Scientists and engineers often need to analyze the energies associated with objects. However, the atoms of all material are not contiguous with one another but are moving in many directions, each with their own potential and kinetic energy. So how can we quantify such system? Thankfully, after many decades of long research, a most useful concept known as internal energy has been developed. The internal energy of a system is defined by the summation all of the energies arising from the microscopic components of a system, which is often summarized symbolically by the equation U_internal = U_potential+U_kinetic, with U standing for energy

Hess’s law

Hess’s law

Hess’s law

12/05/16

“How can we find the change in enthalpy for a chemical reaction without actually performing the reaction?”

Finding the change in enthalpy for a chemical reaction is a rather straightforward procedure, one simply carries forward with the necessary steps and measures the temperature before and after the reaction took place. However, some reactions take an extraordinary long time to perform, or their process is highly volatile. So how can we find the change in enthalpy for such reactions? Well let’s think about it. We know that if we were to take one chemical reaction and reverse it, then the resulting change in enthalpy would reverse in sign. And we know that if we add one element of a chemical equation to the opposite side of an equation containing that element, then they would cancel out. So what if were to take the results of some reactions that we already know, modify them if necessary, and then add them together to fashion the equation of the reaction that we desire? This is the operating principle behind Hess’ law.

To illustrate, let’s examine the reaction Mg(s) + H2O(l) → MgO(s) +H2(g). Since Mg does not react with water, completing this experimentally would be a nightmarish process. However, we can easily obtain the results for Mg(s) +2HCL(aq) → MgCl2(aq) + H2 and MgO(s) + 2HCl(aq) → MgCl2(aq) + H2O. If we were to take the former equation and subtract the latter from it, we would be able to obtain our desired equation. All we need to do is obtain the change in enthalpies for these reactions, and then proceed forward with the mathematics, and next thing you know we would obtain our necessary results!

Change in Enthalpy

Change in Enthalpy

Change in Enthalpy

12/04/16

“How can we measure the change of energy in a thermodynamic system when the system itself changes?”

 

All thermodynamic systems have the summation of the parts of their energy represented by enthalpy. However, the universe is almost never in a static state, and is always changing. Consequently, all thermodynamic systems will be in perpetual change as well. And it turns out that this change in enthalpy has very practical results for scientific use. A change in enthalpy can be quantitatively described by taking the difference of the enthalpy of the system after the change and before the change. If the  enthalpy has gone up, then that means that energy must have been added to the system, making it an endothermic process. If the enthalpy has gone down, then heat was removed from the system and it was an exothermic process. The change in Enthalpy is often symbolically represented using a (delta)H

Enthalpy

Enthalpy

Enthalpy

12/03/16

“How can we model the total energy inside a thermodynamic system?”

 

As a scientist or engineer, if you ever work with thermodynamics systems, then you will have to understand the amount of energythat you are working with. However, how can we represent this concept in more concrete terms? Well, luckily for us, after many years of hard labor, scientists and engineers have formulated the very concept of enthalpy of this very matter. Enthalpy can be defined as the amount of energy stored within a thermodynamic system, which can be symbolically defined as H = u + p*V, with H being the enthalpy, u being the internal energy of the system, p being the pressure and V being the volume.

Energy density and it’s importance

Energy density and it’s importance

Energy density and it’s importance

12/02/16

“How do scientists and engineers measure the density of energy within a system and why is it important?”

Energy is a quantity that is used omnipresently for calculations in all branches of science and engineering. However, energy is more than a theoretical abstraction, and since it is tied to the material universe, it must be stored somewhere in reality, such as in objects. And since objects of the same size can have different abilities to hold energy , we will need some conceptual way to understand this. As a result, scientists and engineers have developed the concept of energy density to represent the amount of energy stored within in object. Energy density is an important concept because when analyzing energy storage mechanisms such as batteries and capacitors, once must take in to consideration the volume vs power limitations that a project might have. To illustrate, let’s say that you want to build an autonomous boat. Since this boat will have no people on board, it will need a mechanism to power it’s systems. However, the boat can not uphold too much weight, or else it will sync. Therefore, when designing such a contraption, engineers will have to choose an energy storage technology with a high energy density.

How heat affects capillary action

How heat affects capillary action

How heat affects capillary action

11/29/16

“How does the temperature of a liquid affect it’s capillary action?”

 

Heat has an effect on a myriad of different properties of materials, but could it possibly have an effect on capillary action? Well, let’s use some of our scientific thinking to find out. We know that increasing the temperature of an object will weaken the intermolecular force of it, and we also know that the strength of capillary action is based upon the relative strength between the adhesive and cohesive forces of a liquid (Which we can symbolically summarize as cohesive force = adhesive – cohesive). So wouldn’t it be logical that if we could weaken the internal cohesive forces of a liquid through heating, that the adhesive forces would have more pull? According to scientific research, this hypothesis proves to be empirically valid!

How intermolecular forces affect the boiling of a substance

How intermolecular forces affect the boiling of a substance

How intermolecular forces affect the boiling of a substance

11/28/16

“How does the molecular bond type of a chemical affect the boiling point of a substance?”

 

In a Chemistry class, you will probably learn that a chemical’s intermolecular force type will have an effect on the boiling point of a substance. However, there is also a good chance that you will never be explained why such a phenomena occurs. And since we were just told a fact without an explanation, we must investigate. Well, first of all, we know that raising the temperature of a substance will increase the kinetic energy of molecules, and if the kinetic energy is raised high enough, then the molecules will be able to escape from their intermolecular constraints. consequently, if the molecules in a liquid are able to escape, then a the free molecules will form a gas, causing the liquid to boil. And since the different types of intermolecular forces have different strengths, then these more powerful bonds will have more force, and as a result the more powerful the type of bond, the higher the boiling point. To give an example, let’s examine two different chemicals with a similar molecular geometry but different types of bond, Water [H2O] and Hydrogen Sulfide [H2S]. Even though H2S has a higher electron count than H2O, since H2O exhibits hydrogen bonding, the boiling point of H2S (-60 C)  is far lower than the boiling point of H20 (100 C)