Wind farms are a common sight these days, but humans have been using wind power for about 2,000 years. It wasn’t always for electricity, however, but to mill grain into flour, operate an organ, or pump water. How does a windmill do any of that though?
When you see a windmill, the part that sticks out most is also the most important: the blades. Blade designs and orientations have changed through the centuries, but they all serve the same purpose and have the same drawbacks. If a windmill has too few blades, the weight of the windmill is imbalanced and will have too much open area, catching very little wind and making it increasingly difficult to actually rotate to blades. Too many blades, and the windmill will be too heavy to easily move in the wind. In either case, power generated by the windmill suffers. Most wind turbines have three blades, and that’s the amount we see most commonly in our whirling windmills class here at AstroCamp.
Number of blades is not everything though, as you can see above; the angle of the blades plays an important role as well. Our windmill has the usual three fins, but isn’t even moving because its blades are flat against the wind. When the wind hits the blades, it just pushes them back. Once you angle the blades, the wind begins to push the blades back as well as up or down, allowing the windmill to spin. The fins must be angled consistently, however, as if blades on opposite sides are both being pushed up, they will cancel one another out and the windmill will still not move.
Adjusting the angle of the blades brought our windmill up to generating over 17 milliamps of current, though campers have gotten over 60 mA with theirs. That’s just the current generated from a tiny windmill in front of a fan, real wind turbines generate enough electricity to power thousands of homes and there are nearly 50 thousand wind turbines in the United States alone.
It’s one of those basic rules we grow up hearing: hot air rises and cool air sinks, but why is that? If you’ve seen our piece on buoyancy, you know that density is one of the key factors in whether an object sinks or floats in a given substance, but a substance’s density doesn’t have to remain the same. The secret is in the name itself: hot air balloon. By altering the temperature of the air inside, we decrease its density, allowing it to float. Since setting off a hot air balloon would be too expensive and a floating lantern is a fire hazard, we showed this same effect by altering the temperature of a helium balloon to prevent it from floating in air.
This all ties back to something in physics called the Ideal Gas Law, which can be expressed as PV=nRT; pressure x volume = number of moles of a substance x the gas constant x temperature.
In the case of a hot air balloon and the helium balloon, “n,” “R,” and “P” are not changing, we can focus on volume and temperature. By decreasing the temperature of the helium balloon, the volume must also decrease. Since density is described as mass divided by volume, as volume decreases, density increases. With enough drop in volume, the helium balloon becomes too dense to float.
After being removed from the liquid nitrogen, the balloon slowly heats back up to room temperature. As it heats up, it returns to its original volume and floats back to the ceiling.
The reverse is true in a hot air balloon, with its density starting equal to the air outside it. As the air inside it is heated, its density decreases to the point where it has so much buoyant force lifting up on it that it can lift not only the balloon but the basket and passengers as well. When it’s in the air, the operator has to make sure the air stays at a consistent temperature for them to maintain altitude, with an increase or decrease in temperature will lead to an increase or decrease in altitude respectively.
WARNING: DO NOT TRY THIS AT HOME. We are dealing with live wires and 120 volts of electricity which can cause fire and/or injuries.
Have you ever wanted to electrify something just to see what would happen? Running electricity of a high voltage through a pickle is definitely dangerous, but also tons of fun! But how is the circuit completed, and why does the pickle glow?
There are two basic types of electricity, static and dynamic. Static electricity is simply a buildup of electrons on a surface whereas dynamic electricity is a steady flow of electrons. Dynamic electricity is what powers things like our home electronics and appliances. There is about 120 volts that can come out of a wall socket, which is exactly what we used to power this experiment.
In order for this experiment to work, we need to be able to complete the circuit. Luckily, pickles are great conductors of electricity due to their high salt content, meaning that electricity can easily flow through them. The salt found in pickles is sodium chloride, NaCl. Electricity at 120 volts is powerful enough to split the NaCl apart into Na+ and Cl-. It then strips the extra electron from the sodium atom producing a photon of yellow-orange light, which is the glow that you see!
If you connect multiple pickles together by a conductive material such as a nail, you will still be able to see the glowing effect. In fact, it is possible to make a long chain of glowing pickles in this manner. However, the more you link the more energy it takes to make it through the circuit and therefore the dimmer the glow will be. How many pickles do you think it would take to no longer see the light?
We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!