# Tag Info

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I don't think it would be practical at all: purely technical problems aside, I am not sure you would be able to ensure safety - we are talking about ionizing radiation, remember?

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Basics You need to be able to generate a pair-creation event and be able to image it well enough to know what it was. Getting a pair conversion event Pair creation calls for the highest energy gamma you can get and as much mass in the chamber as you can arrange. The odds of getting a pair-conversion event are graphed in figure 31.17 of the 2013 ...

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These electron-positron pairs are created by gamma rays. I don't know anything about how to make a cloud chamber, but detecting cosmic gamma rays at the surface of the Earth is very very rare. The atmosphere is very opaque to gamma rays (Source). Cosmic gamma rays burst are commonly detected on satellites orbiting the Earth, but very few make it to the ...

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Second answer, what about the phenomenon of “Quantum Locking”? Right now it is being used to levitate superconductors over magnets, but I am sure you could exploit the phenomenon to transmit torque. Plus, you can put the superconductor on the vacuum side of the seal to keep it cold.

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Take a look at the torque converters of cars with automatic transmissions. They are rotational couplings where the working fluid is completely sealed from both the source and sink environments, so one of those could be vacuum. One shell of the device rotates inside the other, to the outer one could be stationary and form an integral (welded) part of the wall ...

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One standard way is a rotary fitting using a ferrofluidic seal. These are fairly standard parts in your favorite vacuum components catalog. Often used in semiconductor processing equipment.

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They exist, but are rare and as far as I know they always contain 'exotic' molecules that will probably be unsuitable for a science fair. A quick google results in this paper as the major result: Cousins et al. 1997 PRL, 79 (2285) Cousins et al. study the excitation gas in superfluid $^3$He-B and find that it behaves in a non-newtonian fashion.

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Well, there are a lot of different types of particle accelerators. Besides the already suggested cathode ray tube, another rather small accelerator would be a cyclotron. The first one was built by Lawrence and Livingston, "a device about 4.5 inches in diameter used a potential of 1,800 volts to accelerate hydrogen ions up to energies of 80,000 electron ...

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It is not so hard, but it won't be able to generate enough high energetic particles. The best example for a particle accelerator is a CRT (cathod ray tube), which you can find in every CRT monitor or TV. It can generate around 40keV electrons. (LHC generates 3.5TeV protons, thus it is around a million times stronger). Only a particle accelerator isn't ...

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First of all, I'm not an expert, but that can be an advantage in trying to explain the equations in lay terms... Maxwell's equations are these, in differential form: $$\nabla \cdot \mathbf{E} = \frac {\rho} {\varepsilon_0}$$ $$\nabla \cdot \mathbf{B} = 0$$ $$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}} {\partial t}$$ $$\nabla \times ... 3 There are a lot of good suggestions here, but I think some of them are missing the crux of the question; the student needs to learn to prove or disprove a hypothesis by varying parameters. For that, you might need several hypotheses - demo experiments are not going to help for the reason they haven't worked so far; they show a rule working, rather than the ... 2 The gaps just need to be smaller than the wavelength of the UV radiation. Waves can only pass through gaps larger than their wavelength. In symbols$$ L < \lambda  Where $L$ is your gap length, and $\lambda$ is the wavelegnth of the UV radiation. Typically this from is $400$ to $10$ nm, with UVA in the $400$ to $320$ nm range, UVB in the $320$ to ...

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How big is an atom? Fill a sink with water. Find a chemical which, when dropped into water, forms a contiguous floating disk. Drop one drop of this chemical into water. Measure volume of drop and area of floating disk. This provides upper bound on the size of an atom. Falling speed versus mass/shape Drop a book and a piece of paper at the same time. Book ...

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Range of a projectile as a function of launch angle is simple and has a nice "right answer" that you can compare with. I'd start with the simplest: "throw this ball as hard as you can straight forward, then straight up, then at some different angles". Measure the distances. If you can do it easily, set up a video camera and play around with measuring the ...

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There are so many things you could do. Here are just two: Put things on a microwave. See how hot they get after 1 minute on high. Does it matter whether you have one, two, three cups. Does adding salt to the water make a difference. How about vegetable oil and water - do they heat at the same rate. What if you add sugar. Does it heat the same when you ...

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As someone who has a fondness for atmospheric physics, I do enjoy the "cloud in a bottle" demonstration. I'm sure children would enjoy seeing a cloud in a bottle too. All you need is: A 2 litre plastic bottle A small amount of water A match It demonstrates how a cloud forms by the process of adiabatic expansion and evaporates by adiabatic compression. ...

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You could see how the mass of an object affects how quickly it falls by dropping balls of various masses (tennis ball, orange, melon, whatever) from a specific height and timing which of these falls fastest. This will allow you to draw the conclusion that the time it takes an object to fall from a given height is independent of the mass. You could also ...

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I'm assuming the daughter of a chemist has been introduced to the non-Newtonian fluid experiment? "struggles to appreciate how changing parameters in an experiment can be used to prove or rule out a hypothesis" = doesn't understand the importance of the control group? Has the scientific method been gone over yet? This may be a little advanced for 3rd ...

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One that jumps to mind is Hooke's law (extension of a spring). Hang a spring or thick elastic band and load it with increasing weights. See that extension is proportional to load at least initially. A natural extension of that is to also measure oscillation time/frequency. Another one would be Archimedes principle, and play with floating/sinking different ...

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Some basics experiments: Freezing of water. The parameter is the temperature. After that, you could add some salt in the ice. You can show that the mix ice/water have a lower freezing temperature than just water. So you can observe T_fusion as a function of the mass percentage of salt in your mix. You can do the same with other stuff : alcohol, vinegar, ...

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This is not an advertisement. Under the rubric of "do try this at home", I wanted to share one more thing that I discovered after writing my previous answer - but it is so unrelated to that answer that I thought it better to write this as a separate post. I discovered two interesting things. First, when you spin a coin on a hard surface, it "rings" with ...

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On a turning roundabout, if you pull your body in to the middle, it will speed up due to conservation of angular momentum. If you lean out, it will slow down, for the same reason. Now, what about if you lie down flat on a large comfy roundabout with your feet at the centre of rotation and your head pointing out. What will happen to the roundabout speed if ...

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Am I allowed to guess? heated water from the bottom is flowing up the warm sides of the pot, while the cooler water from the top is being forced down the middle of the whirlpool to the bottom where it can be heated? this opposing flows of water have caused a whirlpool that acts in effect as a heat pump?

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I don't mean to take anything away from the previous great answers, but the "simple and to the point" answer is, a very qualified, yes. By qualified, I mean one must know the coin's composition, thickness, diameter(or shape), density distribution, country of manufacture, etc. If we make assumptions and restrictions, then it becomes possible to calculate ...

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AM radio is in a band from about 500kHz to 1500kHz which corresponds to wavelengths from about 200m to 600m, vastly longer than your baking trays. This affects the manner of the interaction between the waves and the trays, and how much the trays will attenuate the signal. For the sake of comparison, your microwave oven is a Faraday cage; it effectively ...

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"There was some gaps totalling a few square cm" A rule of thumb is that if the screen isn't airtight those radio waves will get in - or out

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I'll assume that you were using a radio tuned to a 1Mhz frequency ($\omega = 6.3\times 10^6$ s$^{-1}$) and that the radio was completely enclosed inside $t=3\,$mm of pure iron. There are two important effects to consider. (i) How much power is reflected from the iron surface. (ii) How much of the transmitted power makes it through the iron. To figure this ...

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So, I decided to try it out. I used Audacity to record ~5 seconds of sound that resulted when I dropped a penny, nickel, dime and quarter onto my table, each 10 times. I then computed the power spectral density of the sound and obtained the following results: I also recorded 5 seconds of me not dropping a coin 10 times to get a background measurement. ...

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If you have the dimensions and material of an object, you can compute both the mass and the normal vibration modes. Just the mass is not enough - a large paper "coin" will have a different fundamental frequency than a small tungsten sphere. A summary of everything that comes below - the result of several edits, and including a nice interaction with the ...

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So a plasma globe contains noble gases at roughly atmospheric pressure. The centre of the globe has an electrode contained within a glass bulb (to contain the gases which are otherwise quite good at finding gaps due to their atomic nature). This central electrode is at high voltage (2-5 kV) and oscillates at high frequency (~35 kHz). This capacitively ...

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As a general rule there are three mechanisms by which molecules absorb light: Electronic transitions - visible/uv wavelengths Vibrational transitions - infra-red wavelengths Rotational transitions - microwave wavelengths In solids you don't often get rotational spectra because the molecules usually aren't free to move without interacting with the ...

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