Then I can change the span distance and measure again. For comparison, I will use a numerical model with the same mass and length as the string of beads. In this case, I broke it into 20 pieces. It looks like this:. If you want to play with the code, just click the pencil icon.
I'll suggest a few changes in the homework questions below. Now I can make the span size of my model the same as the beads and compare the tension and vertical drop.
Basic Model For a Hanging Cable. Comparing a Numerical Model to Real Data. Rhett Allain is an associate professor of physics at Southeastern Louisiana University. He enjoys teaching and talking about physics. Sometimes he takes things apart and can't put them back together. Pin type insulators are not economical at operating voltages greater than 33 kV. It is placed on the cross arm of the supporting tower. The pin insulator has grooves on the upper end for keeping the conductor. There is thermal expansion of metals, and in a power line the length will become greater than the installation one.
Wires droop because they have weight, and because the length of wire strung between two poles is longer than the spacing between the poles. Hint: Telephone wires are made up of metals and as we know that metals tend to expand in hot temperatures and shrink in cold temperatures.
The wires are usually made up of copper or aluminum. The wires expand due to thermal expansion, while in winters they contract and become taut. Because the cores of overhead wires are made from copper. The higher temperatures in summer make the copper expand — so the lines get slightly longer. In winter, the reverse happens — the lines contract and tighten up. Hope this was helpful for you.
The electric wires expand due to rise in temperature in the hot summer. Due to this reason,the wire become loose in summer. Electrical wiring is usually covered with layer of plastic to make it safe. As we know that plastic is an electrical insulator and it is readily available and cheap.
So as to insulate the electricity carrying wire, to make it shock free. Most electrical wire is covered in a rubber or plastic coating called insulation. This diagram not to scale depicts the electrospray system, which uses an electric field to create cones of water that break up into tiny droplets. Electrospray is relatively simple to demonstrate with a single emitter-extractor pair, but one emitter only produces 10 7 —10 9 droplets per second, whereas we need 10 16 —10 17 per second.
Producing that amount requires an array of up to , by , capillaries. Building such an array is no small feat. We're relying on techniques more commonly associated with cloud computing than actual clouds. Using the same lithography, etch, and deposition techniques used to make integrated circuits, we can fabricate large arrays of tiny capillaries with aligned extractors and precisely placed electrodes.
Images taken by a scanning electron microscope show the capillary emitters used in the electrospray system. Testing our technologies presents yet another set of challenges. Ideally, we would like to know the initial size distribution of the saltwater droplets. In practice, that's nearly impossible to measure. Most of our droplets are smaller than the wavelength of light, precluding non-contact measurements based on light scattering.
Instead, we must measure particle sizes downstream, after the plume has evolved. Our primary tool, called a scanning electrical mobility spectrometer , measures the mobility of charged dry particles in an electrical field to determine their diameter.
But that method is sensitive to factors like the room's size and air currents and whether the particles collide with objects in the room. To address these problems, we built a sealed cubic meter tent, equipped with dehumidifiers, fans, filters, and an array of connected sensors.
Working in the tent allows us to spray for longer periods of time and with multiple nozzles, without the particle concentration or humidity becoming higher than what we would see in the field. We can also study how the spray plumes from multiple nozzles interact and evolve over time.
What's more, we can more precisely mimic conditions over the ocean and tune parameters such as air speed and humidity. We'll eventually outgrow the tent and have to move to a large indoor space to continue our testing.
The next step will be outdoor testing to study plume behavior in real conditions, though not at a high enough rate that we would measurably perturb the clouds. We'd like to measure particle size and concentrations far downstream of our sprayer, from hundreds of meters to several kilometers, to determine if the particles lift or sink and how far they spread.
Such experiments will help us optimize our technology, answering such questions as whether we need to add heat to our system to encourage the particles to rise to the cloud layer. The data obtained in these preliminary tests will also inform our models.
And if the results of the model studies are promising, we can proceed to field experiments in which clouds are brightened sufficiently to study key processes. As discussed above, such experiments would be performed over a small and short time so that any effects on climate wouldn't be significant.
These experiments would provide a critical check of our simulations, and therefore of our ability to accurately predict the impacts of MCB. It's still unclear whether MCB could help society avoid the worst impacts of climate change, or whether it's too risky, or not effective enough to be useful.
At this point, we don't know enough to advocate for its implementation, and we're definitely not suggesting it as an alternative to reducing emissions. The intent of our research is to provide policymakers and society with the data needed to assess MCB as one approach to slow warming, providing information on both its potential and risks. To this end, we've submitted our experimental plans for review by the U. National Oceanic and Atmospheric Administration and for open publication as part of a U.
National Academy of Sciences study of research in the field of solar climate intervention. We hope that we can shed light on the feasibility of MCB as a tool to make the planet safer. More Heat, Less Sag. Explore by topic. The Magazine The Institute. IEEE Spectrum. Our articles, podcasts, and infographics inform our readers about developments in technology, engineering, and science. Join IEEE. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity.
Enjoy more free content and benefits by creating an account Create an account to access more content and features on IEEE Spectrum, including the ability to save articles to read later , download Spectrum Collections , and participate in conversations with readers and editors. Energy Topic Type News. Cables may help ease the power squeeze by delivering more current along the same rights of way. Topic Type Robotics News.
Topic Type Semiconductors Analysis. Related Stories. Energy Topic News Type. Another interesting tidbit is that power lines can move more power in reasonably windy conditions, as the wind cools down the conductors. Funny stuff Add a comment. Active Oldest Votes. Improve this answer. Keenan Pepper Keenan Pepper 7, 2 2 gold badges 23 23 silver badges 29 29 bronze badges. Copper is very expensive, corrodes and is mechanically weak.
I don't think First Energy does though. So running at high temperatures for a few hours a day, may add up to a catastrophic failure in a few years. I used to work in the transmission line industry and your question is very welcome here. John Alexiou John Alexiou Are the ice levels monitored or modeled "guessed" so that a quick response can come by increasing the reactive power my guess to increase the losses?
I'm sorry that this is a question-comment, but I guess the answer will be short. On top of that there are additional safety factors in order to take into account other knowns. The thing that I'm missing is the mitigation strategies for critical situations, like what to do from the power flow management point of view for the given power line. Particularly "can the ice laden doomed power line be saved by high losses", there is a hint to it in the ampacity chapter..
When loaded with wind and ice sag increases and when the temperature goes it the sag increases further. So forestry control is important to maintain clearances, as well as making sure the tensions do not exceed the support limits.
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