Category: Engineering

Trusses

Trusses

08/28/16

“What is the fundamental framework behind many modern structures?”

Have you ever wondered what exactly makes moderns structures such as bridges and houses supportable? Well, believe it or not, all of these complex structures have their foundations in a straightforward yet ingenious engineering piece, the beam. And not just beams by themselves, but beams arranged in a very particular way. When making edifices, one must take into account that beams have very little lateral strength. In other words, beams do not have much strength to support perpendicular forces. However, beams are very sturdy when it comes to compressive and tensile forces. So in order to build complex structures, beams must be construed in a way that all of the forces are applied at the joints so that all of the forces are either compressive or tensile forces. We can accomplish this by having the beams must be connected only by their joints. This way, all of the loads will be distributed on the ends of the beam, so we can have highly stable structures without having to worry about collapse. This type of framework is called a truss, and is used in all forms of engineering.

Galvanic cells

Galvanic cells

08/27/16

“What is the simplest possible battery?”

Batteries are some of the most omnipresent electrical components in human civilization. However, what is the most simple form of them? Well, in order to do that, we have to put everything into it’s most basic parts.

Well, let’s suppose we have a slab of zinc and a slab of copper, both occupying space in separate dishes of water. Both of them have some of their substance dissolved in the water. The electrons on the zinc solvent want to leave the element, while the copper solvent (with a charge of +2) wants to obtain electrons. If we connect both the copper and the zinc slab with a conducting wire, then the extra electrons on the zinc side will sense the voltage potential on the other side, creating a current, with the zinc side being the cathode and the copper side being the anode. The zinc increasingly becomes oxidized, while the copper becomes increasingly redoxed. However, as this process progresses, more zinc cations will be generated along with the disappearance of more anions, leading to a short life time!. To solve this problem, a salt bridge is instituted connecting the zinc and lead sides. This salt bridge is made up of Potassium Chloride [KCl] in a pseudo-aqueous solution (meaning that it is viscous to a point that the salt will not immediately react with the surrounding elements). As the process goes on and both sides become more charge neutral, the salt will break up bit by bit to have the positive potassium ions replenish the charge of the copper and the negative chloride will replenish the charge of the zinc

This in turn creates a simple battery, called a galvanic cell (Also termed a voltaic cell, after the Two Italian scientists Luigi Galvani and Alessandro Volta, respectively).

Hydropower

Hydropower

08/26/16

“Can water be used to create useful energy?”

Water is one of the most omnipresent substances found on this planet.An entire three-quarters of the planet is covered by it. Water often moves not in small streams but with large flows, piling through it’s path with titanic levels of energy. So one might think, is it possible to capture some of this energy to transfer it into useful forms?

Well, let’s think about how we could do so. First of all, we know that turbines can extract energy from moving fluids to power a generator to create electricity. Second of all, We know that water flow can be controlled through the uses of dams. So what if we placed a damn near a flowing path of water, and directed all of that energy so it would move a turbine that would power human infrastructure? Well, this is the operating principle behind hydropower.

Hydropower is the use of the kinetic energy of water to power electricity. The power generated by a hydropower plant can be calculated with the following equation P=Mu*rho*Q*g*h, with Mu being the efficiency of the turbines, rho being the density of the water passing through, (Kilograms per cubic meter), Q being the flow (Cubic meters per second), g being the acceleration by gravity, and h being the height difference between the inlet and outlet in meters. Hydropower is clean, renewable, and affordable form of energy. Hydropower produces almost one fifth of the world’s electricity, the primary contributors being China, Canada, Brazil, The United States, and Russia. Notable hydroelectric projects include the three gorges damn in China and the Grand Coulee Dam on the Columbia River in northern Washington in the U.S. However, one has to be cautious when developing such systems, and the infrastructure may disrupt local wildlife and natural resources.

In summation, hydropower is a fascinating subject, and engineers around the world are dedicating themselves to the study and application of this form of power.

Smart rubber

Smart rubber

08/23/16

“Are there materials that can “heal” themselves when torn?”

Have you ever had the misfortune of having a rubber material rendered useless just because you’ve torn it? Wouldn’t it be nice to have some form of rubber in which the object can heal itself once it becomes damaged?

Well, how about instead of being in dismay over such an issue, we take action and use our technical mind to solve the problems! First of all, let’s think of the root cause. Rubber materials obtain their strength from the fact that they are composed of multiple polymer molecules being crosslinked through three different ways: Covalent, ionic, and hydrogen bonding. However, only hydrogen bonding can revert to it’s original structure after being deformed. So wouldn’t it be logical that if we only had the rubber composed of hydrogen bonds, then it would be completely mendable?

Well, this is exactly the working principle behind smart rubber. Smart rubber is rubber composed entirely of hydrogen bonds, so that it “heal” itself when necessary (at near room temperature). Smart rubber can be used to create items such as shoes and tires that can repair themselves after intense use. Smart rubber is better for the environment since it encourages less waste. The one downside of Smart rubber is that it is weaker than normal rubber by nature, as the material lacks the extra structure of the covalent and ionic bonds.

Motor armatures

Motor armatures

08/21/16

“What component causes an electric motor to spin?”

We know that Electric motors have two main mechanical parts, a stationary stator that encapsulates a rotating rotor. Now, how is this rotation induced? Well, in addition to having the aforementioned two mechanical components, electric motors has two electrical components. The first electrical component is called the field, which is simply the magnetic field component inside the airgap. This field will turn the armature, which is the primary power producing component in the motor. The armature carries current that is oriented perpendicular to the magnetic field, which in turn will induce a force which will cause a torque to take place. The armature usually consist of several conductive windings for this effect to happen. The field and the armature can be on either on the rotor or the stator but one must only occupy one other.

Resistor coloring

Resistor coloring

08/20/16

“Why do resistors have different colors?”

When looking at resistors, you might notice that they seem to have different colors. Four in fact, all in different bands. What do they mean and what do they imply? Well believe it or not, this different resistor coloring corresponds to different resistance values. This means that users such as yourself can easily find the resistor they require just by looking at the band colors.

The first band (called band A) represents the first figure, the second one t(band b) represents the second figure (some more precise resistors may have an extra band to indicated a further figure), the third band the Decimal multiplier (meaning how much this figure constructed by the earlier bands will be multiplied by), and the final band represents the tolerance percentage (no band means a 20% tolerance level). A chart of the colors and the corresponding values can be found in the picture above

To get a better idea about how this works, let’s do an example. Let’s say that you find a band with the first band colored gray, the second band colored blue, the third green, and the final one red. This resistor will have a value of 86*10^5 ohms, and a tolerance of +-2%. Now go out there, find yourself some resistors, and try to apply these rules to try to estimated the values!

Series and Parallel

Series and Parallel

08/18/16

“How can different elements in a circuit be hooked up and what are the effects on current?”

When studying electronics, one might wonder, “What are the different ways that we hook up different resistors in a circuit, and how do they affect the circuit current itself?”. Well, let’s think about it.

One way we could hook up everything is to directly connect each element in series. This way, the voltage from the power source will pass through each individual part, giving an associated drop at each one. Due to the fact that they are all directly connected, each resistive element will have the same current pass through it. This makes calculating the final current easily, because we can solve symbolically as follows. Let’s say we have a circuit with 3 resistors, all of different values R1, R2, and R3. Each one of them will have the same current I. Because the voltage drop through all of them combined must be equal to the total voltage V, we can construct the algebraic equation I*R1+ I*R2 + I*R3=V. Due to a common factor of I, we can simplify this equation to be I*(R1+R2+R3)=V. We can then divide the voltage by the total resistance to find the current I = V/(R1+R2+R3). This pattern holds for any number of elements in series. Let’s do a numerical example to cement our knowledge. Let’s take R1=1 ohm, R2= 2 ohm, R3 = 3 ohm, and V = 12 volts. If we do our math right, then we should end up with I=12/(1+2+3) → I=12/6 → I = 2 amps.

Another example that we could do is to to elements, hook them up directly to the voltage source, but do not directly connect them, only have them in parallel. Let’s work out the framework for these paradigm. Since each element is directly hooked up the voltage source, not only must it provide a current to go through each element, but the voltage drop must be the same as the voltage source. So how can we find out the current? Well, it’s actually surprisingly simple. First we must notice that each of the elements obtain an individual current, corresponding to the voltage divided by the resistance, or v/r. We must then notice that the total current I will be all of the individual currents added up, I = V/R1+V/R2+V/R3+….Then, since there is a common factor on each of these elements V (as I = V/R), we can divide everything by the Voltage V, to obtain I/V=1/R1+1/R2+1/R3+… , and if we simply notice that I/V is equal to the inverse of the total resistance Req, we can then represent this equation as 1/Req=1/R1+1/R2+1/R3.. We can obtain an equivalent resistance for all of the elements in parallel, and find the total current by setting it equal to the total voltage or I=V/Req, and find our answer! As one can observe, and a parallel setup, the more elements one adds, the higher the current will be, because all of those elements will need to be supplied with the same voltage drop

Electric arcs

Electric arcs

08/04/16

“What are those electric discharges that I see in highly ionized gasses?”

You might be curious what exactlymakes welding work. Well, it turns out to be very simple. All that is going on is that there is a continuous, high density electric current that passes through a gas or vapor with a relatively low potential difference across the conductors. This allows for the high intensity of heat that is used for engineering applications such as welding

Electrical resistors

Electrical resistors

08/14/16

“What causes electrical resistance?”

When working with circuits, you have probably read about how resistance causes a current to slow down. However, what causes this resistance, and how does it work?

Well, these items are simply called resistors. Resistors are simple by construction, being only a ceramic round surrounded by a winding of copper. Resistors are able to causes an impedance to current flow by dissipating power, with the power loss being equal to the square of the current times the resistance, which can be represented analytically as P=I^2*R. Some resistors actually have an adjustable resistance. The surrounding heat can have adverse effects on the resistivity of a resistor, however, some resistors are designed to apply this heat for their daily functioning.