An odd effect on my camera

 I was trying to take a photograph of a sample of rock when I noticed this striped effect on my camera screen. It wasn't visible to the eye.

 My lamp looks like this:

I wondered whether it was an interference effect like Lloyd's mirror but the angles were all wrong. But it occurred to me that it might be that I was detecting the ac flicker of a fluorescent tube. Alternating current would mean it would be flashing 50 times a second. So why does that show up as line on the screen? To understand my theory, look at this photograph that I took from the coach on the Berlin trip

The odd angle on the back of the lorry suggests to me that the CCD on the back of the camera loads in lines from top to bottom. Hence the lorry has moved forward by the time the bottom of the picture is taken. If that's the case, then during an exposure, the light would be on for some lines and off for other lines, giving me my picture. 6 lines would give an exposure time of 0.12 seconds. However, the lines stay horizontal when I turn the camera through 90 degrees. Would the camera read the lines the other way if I turned the camera? Probably not so more thought necessary.

Acid and alkali - making salt

We made salt by mixing two clear and colourless liquids: hydrochloric acid and sodium hydroxide. Sodium hydroxide is an alkali. We started by placing a small volume of alkali in a test tube and added Universal Indicator, which went purple showing pH11. We counted drops of acid until the Universal Indicator went green. It was a neutralisation reaction. We had made an aqueous solution of sodium chloride. To get the crystals, we needed to evaporate away the water. The problem was that the salt would have the colour of the Universal Indicator, so we needed to repeat the experiment without the indicator. Here's the end product.

The experiment works because of the reactivity of the ions in the solutions. Sodium hydroxide contains Na+ and OH- ions. Hydrochloric acid contains H+ and Cl- ions. Na+ is more reactive than H+ because it finds it easier to lose electrons. It bonds more easily to the Cl- ion because that is the smallest of the two negative ions. The result is a cubic crystal lattice like this:

This lattice is a strong shape and that makes the molecule very stable. Stable means lower potential energy. In the same way that water flows to the place of lowest potential energy, so chemical reactions happen most often when they head towards lower potential energy. That's why this neutralisation reaction is able to occur and it is why acid and alkali make salt. Finally, notice that if the Na+ bonds with the Cl-, that leave behind H+ and OH-. Of course, that's H2O!!

Queen of the South and the cost of running floodlights

I took this picture at the Queen of the South ground in Dumfries. I was interested in how much it might cost to run the floodlights for a game. So:
1. Count the number of lights on the pylon in this corner of the ground.
2. Estimate the total number of floodlights in the ground.
3. If one light is 2kW, work out the total number of kW for the whole ground.
4. State how many hours you think the lights will be on for an evening game, giving your reasons.
5. Then calculate the total kilowatthours - the total kW x the hours.
6. If 1kWh costs 10p, how much will the floodlights cost for one game?

Haweswater: a novel and some volumes

I have posted about Haweswater several times in the last few months so I was interested to find this novel in the school library, by a Cumbrian author. It is set in the old hamlet of Mardale, which didn't quite emerge from the water this year, at the time Manchester Corporation were deciding to start building the reservoir. On page 50, it is suggested that the volume of the new reservoir will be twenty thousand million gallons. Now there are 0.004546 cubic metres in 1 gallon, which means the figure in the book equates to 90,920,000 cubic metres. Wikipedia gives a volume of 76,600,000 cubic metres http://en.wikipedia.org/wiki/Haweswater_Reservoir so the current stated volume may be less than originally envisaged. It also states that the volume is the same as 62,100 acre.ft. What a wonderful unit! An acre is about half a football pitch so it is a very wide and not very deep volume. In August I estimated that the reservoir was down by about 6 million cubic metres. That's not far off 10% of the stated volume so perhaps not a bad estimate http://www.wigtonphysics.blogspot.co.uk/2014/07/will-mardale-appear-from-haweswater.html Finally Wikipedia has introduced me to a concept called "residence time": the length of time it takes a water molecule to pass through the reservoir. This is 500 days. Nearly teo years...

Have a go at Super Planet Crash

There are very frequent announcements of the discovery of exoplanets. These are planets that go round stars other than the Sun. You can't see them with telescopes. They are so far away and the light reflected from them is so dull. Instead they are detected by picking up the small dimming effect when they pass across the face of their star, or by the way they make the star slightly wobble as they orbit. Both of these effects are greater if the planet is the size of Jupiter. Since we can't study systems like this directly by observation, computer modelling helps. Here's one such programme, made into a game: http://apod.nasa.gov/apod/ap150112.html Click the link and have a go at Super Planet Crash. My first few goes ended in catastrophe. I then played safe by installing 11 Earth sized planets and my system lasted 500 years. I got 115,766 points.

Then I tried again with a couple of ice giants and a giant planet thrown in as well. It was stable for 500 years and I managed 295, 400 points. Can you beat that? The game goes slowly so you might want to press fast forward when you are sure that it seems stable.

Take the physics teacher bowling

I hadn't been bowling for years so I'd like to blame overthinking it for my defeat. The balls have different masses. So should I choose a lighter ball that I can bowl faster or a heavier one that I find harder to shift? Would there be much difference in their momenta? In the end, I found that the faster I tried to bowl them, the less accurate. But I was struggling to get "strike" even with a heavy, slower, accurate ball. I could knock over 8 or 9 but not the elusive last couple. At the far end, is it momentum or kinetic energy that is important. If it is KE, then perhaps speed is more important because that squares. But I had less success with the lighter balls. Also, I get tired so it ceases to be a controlled experiment, More research needed.

Spark counter

The spark counter is a series of thin wires a few millimetres above the surface of a silver metal disc. The potential difference is adjusted to a few thousand Volts. The electric field strength in the gap between the wires and the plate becomes so big that it forces the air to conduct and you get sparks. You get this to happen and then turn it down slightly so that it is almost bu not quite sparking. Then you bring in the alpha radioactive source, as shown in the picture. The sparks come back. But you get nothing with beta and gamma. This is because the alpha particles are able to ionise air molecules, allowing the air to conduct and producing sparks. Putting paper in the way stops it.

Butane gas stove at low temperatures

 

 We took our new gas stove to Silloth for a cup of tea. It worked well in our kitchen but didn't perform well outside. Eventually I remembered that butane is not good in low temperatures. The reason is that the boiling point of butane is -0.5 degrees Celsius. It is harder for the butane liquid in the canister to evaporate at low temperatures. It is the vapour that burns so the flame is not as strong.

 

 

 The problem is made worse by the adiabatic cooling of the expanding gas as it leaves the cylinder to go into the burner. It chills the canister further. Evidence of this was a lot of condensation on the outside of the tin.

 

Adiabatic expansion - the Lynx Effect??

Why do aerosol body sprays feel cold? It's to do with the First Law of Thermodynamics. Temperature and heat are not the same thing. Temperature is a measure of the internal energy of the molecules - oh go on - let's call it how much they wobble. There are two ways to make them wobble more - hit them or heat them. So heat is energy that goes in to make them wobble more. We can hammer them to make them wobble more - that's called doing mechanical work. Now when the aerosol spray comes out of the nozzle it expands and thus does work on the air around it. The energy for that expansion and work has to come from somewhere. It happens so fast that there is no time for thermal energy to flow into the spray. We use the word ADIABATIC for that case when there is no time to get the thermal energy in and all the changes are wrought by mechanical work. So the molecules steal internal energy from the molecules in the spray to give the energy for the expansion. This means that there is less internal energy and the temperature has gone down. The spray feels colder.

Another stationary wave

At Scale Hill near Crummock Water there is this weir which I think is used for flow measurement. The bottom of the stream comes up, making the water shallower. The water flows at the same volume flow rate, so it must move faster to get through the decreased cross section. It then speeds up down the ramp and goes from transparent laminar flow to turbulent flow. The Reynold's number must go above 1000. A stationary wave forms at the bottom of the slope. It's amazing to think that the individual water molecules flow through it quickly but the shape stays the same for hours.

Seeing things? Purple clouds

It hasn't photographed as well as I'd hoped but for much of the morning on Sunday the clouds above Skiddaw looked a definite shade of violet, perhaps lilac. It was heading towards the middle of the day so we're not talking a sunset effect, which is all I've got when I've tried searching on the Internet. The Sun was behind me. This effect was not visible on the clouds on the same side as the Sun. So more observations will be needed. My companions agreed that it was true, but is it a physiological effect? Is it to do with the snow cover on the mountains? Is it to do with scattered light coming down through the clouds or is it light scattered back from the snow fields?

Trying to make a Riemann surface

I'm attempting to read Roger Penrose's 1000 page epic called The Road to Reality. I can follow the maths for the first 120 pages but then I'm into stuff that is new for me: Riemann surfaces. I think we're being softened up for General Relativity. It starts with the idea of an imaginary number. Think about the square root of -1. It can't possibly exist because when you square a positive number you get another positive number; when you square a negative number you also get a positive. Nothing can be squared and end up negative. Ah, but that's just for ordinary numbers. Let's invent a number i, an imaginary number that squares to become -1. Then we can get complex numbers that are a mixture of ordinary numbers and these new imaginary numbers eg 4+i or 7+2i. These then can be plotted on graphs with the ordinary numbers of the x-axis and the imaginary numbers on the y-axis. It's called the complex plane. Riemann had the idea of cutting sections of the plane and gluing them together for the cases where functions lead to more than one answer. An example of this would be an ordinary square root eg square root of 4 can be either 2 or -2. Roger Penrose has a diagram like the picture below suggesting that you can glue these bits of the complex plane together. I couldn't figure it out so I had to have a go. You glue together the opposite sections with the same pattern. 

In the end I found it best to intersect them, like an x. When I did that repeatedly I found that I could keep a pen on the paper all the way down to draw a continuous spiral. I made my first Riemann surface. I don't fully understand this yet.

I found a short film someone made of a similar attempt with two surfaces https://www.youtube.com/watch?v=mIOvmCyT4DQ

Lenticular clouds and stationary waves again

 I spotted this lenticular cloud hiding the Sun when we were coming back down the Sticks Pass to Thirlmere. Lenticular clouds are supposed to be formed when wind blows over mountains and the disturbance sets up stationary waves in the air. The water vapour gets trapped between the bottom and the top of the wave shape, forming a lens shaped cloud. What occurred to me today was that if it is a stationary wave, the cloud should stay in the same place. I took the picture below 15 minutes later.

 Lower level clouds have moved in from the north on the wind (from the right in the picture) but the lenticular cloud has stayed in roughly the same place. I was using the position of the Sun to show that the cloud was in the same place but realised that the Sun moves. When I did the sundial research last month I found that the Sun moves 15 degrees in one hour. It will move almost 4 degrees in 15 minutes. That is 4 little fingers.

 Thumb to little finger turns out to be 25 degrees.

I kept watching. The lenticular cloud did stay in the same place as lower cloud came in and obscured it. An hour later the sky cleared again and there were still the remnants of the lenticular cloud in the same place. Stationary waves, then.

Biological washing powder, enzymes and kinetic molecules

Read the small print on the side of the box! If you read the second and third lists of ingredients, you will see that they have listed 3 enzymes in the washing powder: amylase, cellulose and protease. For example, protease digests protein. Suppose you spill egg onto your clothes. The protease would digest the protein in the egg stain making it much easier to wash out. Biological washing powder contains enzymes. Enzymes are biological catalysts. In other words, they speed up reactions without being used up themselves. They do their work by a lock and key mechanism. Molecules of the correct shape fit into active sites on the side of the enzyme. Then they can react more easily because fitting into the enzyme reduces the amount of energy needed for a reaction to happen (this is called the activation energy). Enzymes are made of protein. If you overheat them, you destroy the special shape of the active sites. We say that the enzyme has been denatured. So you mustn't let the washing water get too hot. Biological washing powders work faster than ordinary powders at lower temperatures. At cold temperatures even enzymes work slower because the molecules that are going to react (called the substrate) have less kinetic energy and are moving around more slowly. The slower they move, the less frequently they collide with other molecules, so fewer reactions happen. Also there is less energy in the collisions so even if they do collide they may not have enough energy to react. Biological washing powders have gone out of fashion because they are often blamed for skin irritation.

Mexican hat potentials

I've been getting my head round the Higgs mechanism. I'm not there yet but here's a summary of some of the stuff that I have heard. There is a Higgs field throughout the Universe. The potential associated with it has the shape of the sombrero hat above. The wooden sphere is a particle. It is just about possible to balance the sphere on the top of the hat. Then there will be perfect symmetry. But it is not stable. If it were stable, we'd have a mass-less Universe. However, it isn't stable and symmetry gets broken. The particle looks for a local minimum. Now there is some form of symmetry in the ability of the sphere to roll around the brim. That could be analogous to the massless photons which are the exchange particles for electromagnetism. I followed the lecture about that far. It was then suggested that if the sphere were to try to go up and down the slope, that would account for the W and Z bosons of the weak interaction having mass. It's beginning to make sense to me but we are not there yet!

Bloomery slag by Coniston Water

 I was walking down the side of Coniston Water when I found rocks like these on the shore line. I knew that there had been iron furnaces in the area centuries ago and I knew that they were called bloomeries. I looked it up and found out that they were homemade heaps of charcoal carbon and iron ore insulated to get hot enough. It is a form of smelting and works because the carbon burns in limited oxygen and produces carbon monoxide. This is hungry for oxygen which it then steals from the iron oxide in the rock. The iron oxide is reduced to iron. Carbon dioxide is made and goes into the air. The iron and the rocky remains of the ore form a molten slag at the bottom which hardens into this slag seen below.

 I wondered at first if it was actually iron, so we tested it with a magnet. It didn't stick so no evidence for iron there. I then set out to measure the density.

 I weighed the rocks and then put them into a displacement can. I measured the volume of the water displaced.

The bigger rock was 507 grams and 200 cubic centimetres. Density = 2.5 grams per cubic cm. The smaller rock 285 grams and 120 cubic centimetres. Density = 2.4 grams per cubic cm. Iron itself has a density of 7.8 grams per cubic cm so if there is any iron here, there's clearly not much. Apparently the slag was then reheated to get the iron. This produced wrought iron.

Photosynthesis and diffusion

There's not much light at this time of year and only a few hardy plants retain their leaves and continue to do photosynthesis. In order to do photosynthesis, they need to get carbon dioxide into the leaf. They do this by the process of DIFFUSION which is actually a bit of Physics. In a gas or a liquid, the particles are in constant random motion. If there is a group of particles all together, the random motion will tend to spread them apart. Thus diffusion is when gases or liquids move from where they are most concentrated to where they are least concentrated. Look at my box diagram of the leaf. There are far more black dots representing carbon dioxide in the air underneath the leaf than there are in the spongy mesophyll layer. Carbon dioxide moves from where it is most concentrated underneath the leaf to where it is least concentrated inside the leaf.

Another pylon observation

I've posted a lot about pylons because they are a very visible piece of Physics. I have been working on learning to see things. I have been to good at looking but not seeing. Things are so familiar that I don't notice details or changes. So it was that I finally spotted that the wires on these pylons are held up by double sets of insulators. Observations lead to questions. Is it because of the weight of the 4 wire parallel bundles? It can't just be that because I have since seen 4 wire bundles held by single insulators. Is it because it is 4 wire bundles over a longer distance and thus heavier? It might be, because I think the pylons were at 300m separation here. I will make further observations to see if I can come up with an answer.

Haweswater up and Hayeswater down

We found ourselves back at Haweswater. I recorded the retreat of the waters during the dry spell. http://www.wigtonphysics.blogspot.co.uk/2014/07/will-mardale-appear-from-haweswater.html and http://www.wigtonphysics.blogspot.co.uk/2014/10/return-to-haweswater-and-mardale-whats.html . I calculated that it would need about 1.5 metres of rainfall over the catchment to refill it. It has rained a lot recently and the reservoir is full again.

We went past Hayeswater when we went up High Street on Boxing Day. They have done as they proposed and removed the dam. The water level has dropped by about 2 metres.

The lake is about 1km long by 0.25km wide. That means that 500 000 cubic metres of water have been lost. My house uses 0.2 cubic metres a day. That volume of water would supply several thousand houses for a year.

Wigton didn't flood

A couple of days before Christmas, we heard reports that Station Road had flooded. It had been raining AGAIN for a long time. Fortunately the reports were wrong. The Wiza was still 1 metre below road level. A constant stream flow exerts a force on an object by applying Newton's Second Law in this way: instead of F=d(mv)/dt which is rate of change of velocity, write F = v.dm/dt because the velocity of the stream is constant. So force = velocity x mass flow rate. Look what happens when the stream hits the inflow from the side pipe. The incoming mass of water has enough inertia to stop the flow down the right hand side of the stream. The force as calculated above is enough to bend the incoming flow into the correct direction. The water was heavily silt-laden and angry that day but the water is pollution-free and supports Kingfishers and Dippers.

What is the mass of copper in Oxford's lightning conductors?

This is a view of a spire on Exeter College from Broad Street . You can see Anthony Gormley's Iron Man sculpture on top of Blackwell's Art bookshop. They'd even put a Santa hat on it! So I looked at the lightning conductor. Say 30 metres long and with a cross-section of 2cm x 0.5cm. The volume comes out at 0.003 cubic metres. Copper has a density of 8960 kg per cubic metre. I was surprised - that is more than iron! 8960 x 0.003 = 27kg. Now how many spires are there? Can't find that on the Internet. Say 30 colleges. That would almost give a tonne of copper. But many buildings have more than one lightning conductor. Then there are churches and mosques... Oh and what counts as Oxford? So some defining of terms to be done...

Dynamo in Patterdale

We went to climb Place Fell at Patterdale. You can just about see it in the background. A rarer sight was this wonderful bicycle dynamo. They are very out of fashion. I had one when I was little. The idea is that the small wheel rubs on the tyre and turns a coil in the larger silver cylinder. There is also a permanent magnet in the cylinder. The rotating coil cuts the flux of the magnet. By Faraday's Law, the size of the induced emf is directly proportional to the rate of flux cutting. If you pedal faster, the rate of flux cutting is bigger and the induced emf is bigger. In other words, the light shines more brightly. This is a disadvantage of the system. Also, the light goes off completely when you stop. I have just read that this should properly be called a magneto because it does not contain a commutator to make the current go in one direction like a proper dynamo: this produces a.c.

Inertia for Christmas

I made this doorstop for Mrs B for Christmas. Hidden inside is a large pebble surrounded by bubble wrap. The pebble has a large mass and by Newton's 2nd Law F=ma, large mass means small acceleration ie large masses don't move very easily. The m in F=ma is called INERTIA. The doorstop needs a lot of inertia so that the door doesn't move. The other use of m is as GRAVITATIONAL MASS in Newton's Law of Gravitation. Both versions of mass have the same measurement in kg. As far as I am aware, people are still trying to figure out why. But in this case we can say that the attraction of the Earth on the gravitational mass gives the doorstop WEIGHT. The normal reaction force (N) is equal in size to the weight. Frictional force = coefficient of friction x N. I think there will be a large coefficient of friction between the carpet and the felt thus making the doorstop even harder to move.

Exothermic epithany in Grange

With Epithany a few days away, here's the Nativity display in Grange-over-Sands. It's been a good year for knitting. We found some lovely guerilla knitting in Seascale in the summer. I'm still thinking about the Physics of knitting! But note the white pot in the corner of the display case in the picture. It will contain something like anhydrous calcium chloride to absorb water vapour from the air and thus stop condensation on the glass. The absorption is an exothermic reaction. It needs some activation energy from somewhere but then the reaction is just like falling over. The chemicals go from a higher energy state to a lower energy state. Potential is lost and is transferred as thermal energy. Potential is usually given a negative number in Physics, This is why I was confused a few years ago when I had my class adding up bond energies for such a reaction. The products' bond energies were bigger than those of the reactants. I realised that you could only claim lower potential energy if the energy was given a negative sign.