Recent content by tech99

  1. tech99

    High School Pumping water upwards into a large water tank

    The only pressure required is the head of water from the water level in the top tank to the ground. Not very much. However, if a leak occurs, then a tonne of water will pour out. Why not fill the top tank from the top, with an air gap, so nothing can escape?
  2. tech99

    Undergrad Why is water pressure increased in a plastic bag in a bucket?

    I have tried to read all the replies, but no one seems to have suggested Osmosis. When the clay is placed in bag of water, salts from the clay will dissolve in the water in the bag and form a solution. As this solution is more concentrated than the water in the bucket, water will pass through...
  3. tech99

    Graduate Physical intuition for FSR dependence on cavity length d in a scanning Fabry-Pérot interferometer

    Regarding the spacing of resonance as you vary the wavelength (or frequency). Imagine a low frequency analogy. Take transmission line 5m long with a short circuits at each end. Apply some energy at frequency that can be varied from zero upwards. When the wavelength becomes 10m, corresponding to...
  4. tech99

    Graduate Physical intuition for FSR dependence on cavity length d in a scanning Fabry-Pérot interferometer

    If you change wavelength, the resonances actually occur at fixed intervals of frequency, so are not exactly uniform wavelength intervals.
  5. tech99

    Why must residential electrical systems be connected to Earth (soil)?

    Isolated systems are used for safety on construction sites etc. A transformer is used where the secondary is not connected to earth. A problem arises, however, if the system gets very big and an accidental connection to earth occurs on one wire. Then the system is dangerous, because if someone...
  6. tech99

    Four L-shaped members: Mechanical Analysis Problem

    I was assuming that the supports were knife edges so that the structure could lift off.
  7. tech99

    Four L-shaped members: Mechanical Analysis Problem

    My ideas are as follows:- If we are to ignore weights, the structure cannot be in equilibrium. So we must assign a weight W to the total structure and we have a centre of mass located on the vertical centre line. The structure acts exactly the same a a block of wood; you do not need to analyse...
  8. tech99

    Graduate Unexpected irregular reflection signal from a high-finesse cavity

    Is the spectrum analyser set to a very narrow bandwidth so that the problem is exaggerated? You seem to obtain a bandwidth of just a few Hertz. Could the cavity be subject to acoustic or mechanical vibration?
  9. tech99

    High School Thought Experiment on Charge Carriers and Electrical Conduction

    An example of a device where positive and negative charges flow in opposite directions is the demountable discharge tube made by Teltron, https://www.healthandcare.co.uk/student-tubes/teltron-discharge-tube-s.html. This has a screen at each end, one showing the negative beam and the other the...
  10. tech99

    High School Where does the figure for a proton's rest mass come from?

    I think the basis of the first understanding the proton was the cathode ray tube of Eugene Goldstein in 1886. In essence, the tube was a simple mass spectrometer, also used by J J Thompson to study the electron. I understand that the Penning trap was not made to work until 1959.
  11. tech99

    Undergrad Mechanism of Energy Conservation in Zero-Amplitude Sum of EM Waveforms

    For the case of a standing wave, there is no net flow of energy - the energy is stored. The electric and magnetic fields are no longer in phase, but in quadrature, and the nodes and antinodes for electric and magnetic fields are physically displaced from each other by a quarter of a wavelength.
  12. tech99

    Undergrad An Imagined Diffraction Grating

    I think what is being described is a zone plate.
  13. tech99

    Curving of gravitational field lines

    Is not the shape of the field simply the superposition at every point of radial fields from more than one body? This gives the curvature.
  14. tech99

    Automotive Looking for dyno verified experiences with turbocharged 2-strokes

    There is an excellent book called Tuning for Speed by Phil Irving.
  15. tech99

    What Caused the Recent Power Outage in Spain, Portugal, and Southern France?

    I think the view is that small events occurred and there was insufficient stored energy in the system to cope with it, so more rotating machinery (or electronic equivalent ) will be required.