Recent content by tech99

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.

I think what is being described is a zone plate.

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.

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

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.

I think my own method here is to work with an electrical analogy. (Of course, it is only my familiarity with electricity which makes me do that, because the equations are equivalent). An analogue of compliance is capacitance. So you can draw a network of six capacitors having values equal to the...

Wind will exert a force even on a static object, due to the change in momentum of the air particles, so no flow past the door is necessary. I remember from the days when we used Imperial units that the pressure exerted by a 10 mph wind on a flat surface was approx 0.4 pounds per square foot. It...

When you dip anything into the tank, it has upthrust due to its displacement volume. If you hold the object rigid, then there is an equal downward reaction force on the balance. The weight of the object is not relevant if the object is held rigidly.

All that is necessary to obtain the volume is to put the tank on a balance. No need for an overflow of any sort. Push the antlers down into the water until covered, not touching the bottom, and note the change of reading on the balance, in grams. That is the volume of the antlers in cubic...

I have noticed that on a small scale, many metals will allow re-charging, including Aluminium in alkali conditions.

A child could insert a metal object. Why not have a shutter to close the live terminal, as in the UK plug system?

I noticed a contractor making a big mistake whilst tensioning the supporting guys (or stays) of a big radio mast. To do this they placed a Newton force-meter (called a dynamometer) in line with the stay. They then pulled tension on the stay (using a chain puller) until the Newton meter showed...

You can buy a portable compass/sundial here: https://nauticalia.com/collections/replica-navigation-instruments/products/sundial-for-travelling They also sell a portable astrolabe so you can find position (to some extent).

The "mirror drum" must be very perfect optically, difficult to achieve I think.

The initial beam from the laser must have finite diameter for it to work I think, that is why I suggested a first, round concave lens as a spreader. The final lens need to be concave cylindrical.