Phase difference for Teeside Wind Farm

 Looking along the lines of turbines from Hartlepool South Pier, I realised that the turbines were not in phase. Some had blades at the top whilst some were pointing at 10 degrees. However, this amount of phase was not fixed. As I watched, they came in and out of phase. If they had maintained the same "out of phase" we could have said that they were coherent -  a fixed phase relationship.

The next day we went to North Gare and I was able to time some of the turbines. The time periods were so close that I had to time 5 revolutions to get the differences. Three different times for 5T were 35.20s, 34.67s and 40.54s. The time periods are therefore 7.04s, 6.93s and 8.10s. The differences might be due to nuances in the wind speed in different parts of the array,

Haze and humidity at Loweswater

We climbed Low Fell above Loweswater. Although the sky was cloudless, the visibility was poor. We could just about make out Great Gable about 10 miles away. That whiteness is characteristic of Mie Scattering from water vapour that I have posted about before. I was wondering whether it was to do with this current warm air from the Caribbean. Is it that it holds more water vapour than cold air and so is the humidity actually high today, even though it is warm and dry? I checked and the reading for humidity at Keswick was 71%. But then I found this: https://en.wikipedia.org/wiki/Visibility The visibility in the picture can't be called HAZE because you can see further than 3 miles. The earlier part of the article discusses the derivation of a rigorous formula to calculate the distance that should be able to be seen. That will take some thinking about.

String cloud in Hartlepool

If you enlarge the photo, just up and right of the top of the nearest street light there is some faint wispy cloud. The picture hasn't quite conveyed what I saw but there seemed to be thin delicate lines of cloud like strings. This is a minimal form of the mackerel sky I've posted about before. It isn't lenticular cloud but I know that lenticular cloud is caused by stationary wave patterns where vapour condenses into the antinodes. This is such a regular periodic pattern with condensed vapour  between clear gaps that I'm wondering if it might be some kind of stationary wave.

Abergwyngregin and the Foehn Effect

I've posted before about the model of the Aber valley that we found when we went to the Aber Falls. Abergwyngregin at the foot of the valley has been in the news because of some very high temperatures recorded at this time of year. It was the subject of the weather column in The Times newspaper yesterday. The reason for such high temperatures on the north coast of Wales is given as the Foehn Effect https://www.youtube.com/watch?v=pJqQoUXMquQ https://en.wikipedia.org/wiki/Foehn_wind There are several parts to the warming effect but the first part is that as air rises, the pressure is lower so the temperature falls and this means that water vapour condenses. The change of state releases latent heat - the heat energy is the reason why the top of cumulus clouds are lumpy when the bottoms are flat. This latent heat warms the air. The process is irreversible because the water leaves the air as rain. In the case of Abergwyngregin, the rain falls over Snowdonia and the warmer, drier air sweeps down the valley. Drier air means more sunshine so making it warmer still. The film and article cited give the other components to the warming. I now need to figure out why Wigton doesn't seem to benefit from the Lake District mountains in the same way.

Specific heat capacity of water

To help us obtain an accurate value for the specific heat capacity of water, we put insulation round and on top of a beaker of water. We weighed the water and measured the temperature rise for the water over a 15 minute period. We calculated the energy we put in by using E = ItV so that's current from the ammeter x time in seconds x voltage. Then specific heat capacity = E/(mass x temp rise). No insulation would have meant a smaller temperature rise for the same energy and hence a value for SHC that would have been too big. Accurate means getting the right answer.

Syncline: Great Orme

We walked under the impressive limestone cliffs on the Great Orme at Llandudno. Look at the angle of the layers in the photograph. Limestone is sedimentary and must be laid in horizontal beds on the bottom of the sea. Earth movements can then bend these layers. Here the layers are heading downwards. The Great Orme is said to be part of a syncline, where rock goes down on one side and then comes back up. I learned a new term researching this: Dinantian. The part of the Carboniferous age when these rock were made. http://geoscience.wales/wp-content/uploads/2016/12/Llandudno-August-Field-excursion.pdf

Absorbing wave energy at RSPB Conwy

Back to look at the waves on the pond again. Once again, the wind was driving in from the south so the waves were coming towards me. But notice how they stop. I'm guessing that there are plants submerged just below the surface at this point, but whatever it is stops the waves. Something must be either absorbing the energy or reflecting it. Maybe it's like when ultrasound has goes from one medium to another. If the difference in wave speed is big then the majority of the waves are reflected back and only a few are transmitted.

Internal energy in a gas and gas pressure

We have a model of an ideal gas which has ball bearings in a clear Perspex tube which are agitated when a motor hits a rubber floor. The ball bearings then hit a polystyrene block so hard that they make it levitate. Pressure is caused by the rate of change of momentum of the balls over unit area. In this picture, the ball bearings are not visible because they were moving so fast. The internal energy of a substance is the sum of the kinetic and potential energies of the particles. For a solid, bond energies contribute to the potential energy. It is much simpler in a gas as there are no potential energies to take into account, so the internal energy is the sum of the kinetic energies of the gas particles.

Convolution and Carl Stone

I was listening to an interview with the composer Carl Stone on Hear and Now on Radio 3. Here's the link but it's only valid for a few days more https://www.bbc.co.uk/sounds/play/m00022k6 The first piece is called Hatiya and he describes it as being a CONVOLUTION. Now that's a term from Mathematics that is used in Physics. See https://en.wikipedia.org/wiki/Convolution If you scroll down to the animated box, it is particularly helpful. Essentially, you seem to slide one signal over another and integrate to find the common area. That common area is then plotted as a new function - the convolution. Carl Stone has taken a piece of Algerian music and then moved a piece of wetern classical music through it - in a way analogous to the animation in Wikipedia. The result is interesting and helpful to understanding convolution.

Meridian Owl at Grizedale

This sculpture in Grizedale Forest is called "Meridian Owl". It revealed a misunderstanding I've had about the word "meridian". I'd thought that the Greenwich Meridian was the only meridian. In fact, any north/south line of longitude that passes from pole to pole is a meridian. So you are always on a meridian. The Greenwich Meridian just happens to be the one chosen by humans to be the zero.

A rather wooden television in Grizedale Forest

We loved this sculpture in Grizedale Forest, set up like an old-fashioned front room. It had been there 3 decades so the television set was a traditional vacuum tube version. In these, the screen was the wide end of a glass vacuum tube. The narrow neck of the tube was hidden in the cabinet-back of the set. In that neck was a thin wire that had a small voltage through it to get it glowing. This gave electrons enough thermal energy to be "boiled off" the wire and into the vacuum. A nearby cylindrical metal anode was set to up to +6000V and attracted the electrons. The inside of the glass tube was conducting and also at this large positive potential which allowed the electrons to pass through the anode without sticking to it. They hit the screen, which had a fluorescent coating, lighting it up. The beam was moved around the screen using vertical and horizontal electromagnets in the neck of the tube. They moved the beam so fast that the single beam seemed to be lighting up the whole screen.

What does Quantum Dry mean?

What has QUANTUM got to do with an anti-perspirant? The history of the use of the word in Physics makes interesting reading https://en.wikipedia.org/wiki/Quantum I hadn't realised that it had been used by physicists before Max Planck. Also that the Latin root is Quantus meaning "how great" presumably to do with size. So is that what is meant on this product? I wonder if it has to do with the popular idea of a quantum leap rather than the idea that dryness comes in discrete lumps. The quantum leap is said to be the jump from one electron energy level to another in Bohr's atom rather than a gradual change in energy. Quantum energy levels in atoms represent tiny energy but in the popular notion, a quantum leap is a sudden and abrupt leap forward.

Boyle's Law with a sealed syringe

we did an experiment using a syringe that had been melted shut with a sealed mass of air inside. We hung weights from the plunger and measured the length of the air column, with got bigger as the weight increased. The cross-sectional area of the syringe was 2 square centimetres. I made a real hash of interpreting the results but I've sorted it out now. The initial air pressure inside the syringe before any weights are added is atmospheric pressure, which is 10 Newtons per square cm. As you add weights to the bottom, you are actually decreasing the pressure because as the volume increases, the number of collisions per second on the sides of the syringe decrease. The volume of the air column is given by the length of the air column x cross-sectional area. The results came out like this:

Every time, the pressure x volume comes out at a constant number, which in reality is nRT or number of moles of trapped air x molar gas constant x temperature in Kelvins. The slight variation in the constant is due to rounding errors.

Transformers

We made these simple transformers in class. This was a step-down transformer with more turns on the primary coil than the secondary coil. It makes the secondary voltage smaller than the primary voltage. Many years ago, classes were somewhat underwhelmed by the concept. They thought that electric current flowed from the primary to the secondary through the iron core. Now I emphasise that the wires are insulated so that is not possible. Thus we now get to have a discussion about the flux in the core. As I understand it, Faraday called it flux because he thought it moved like a current. Apparently it doesn't but this fiction is a brilliant predictor of what actually happens.

Mass and weight AGAIN!

Every physics teacher spends a large part of their life complaining about the casual mislabeling of weight. Mass is the amount of stuff an object is made of, measured in kg. Mass is interesting because it can be thought of an inertia, the resistance to accelerations, or as the stuff on which gravity pulls. The pull of gravity on mass is called WEIGHT and is equal to mass x g. Hence the weight of this kettlebell is actually 981 Newotons.

Dull vapour trail at Maryport

Can you see the aeroplane vapour trail in the middle of the picture? It was dark. The plane was on the sunny side of the cloud by this point. I have seen this sort of thing before when a shadow of the vapour trail was projected onto the thin layer of cloud below but there is none such here. I don't think this can be a shadow because I know that shadows can't project onto thin air. So I'm guessing that the vapour trail is reflecting the duller scattered light from the cloud.

The Moon, Venus and my camera

I tried to photograph the lunar eclipse two weeks ago but got only a black image. My lovely cheap camera is not so good in low light so I was surprised that it was able to pick up Venus left of the Moon the other day. A little research shows that the camera contains a CMOS detector, not a CCD. I have taught about CCDs for years but hadn't realised that there was an alternative. CMOS is an abbreviation I know from transistors. Apparently the light sensors are made by the multiple transistor production process and are thus very cheap. Each pixel has its own tiny amplifier which means that there are more areas on the sensor that don't pick up light. Also the detection has more "noise" than CCD. However, they use less power. No wonder my batteries are lasting longer. https://electronics.howstuffworks.com/cameras-photography/digital/question362.htm