# Tag Info

-1

It seems like 60 Hz may have been selected instead of 55 or 75 simply because there are 60 seconds in a minute and so 60 cycles per second seemed a comfortable number. During the early days of distributed power transmission the frequencies and voltages would have been all over the place. The limits of what was safe and convenient would have been developed ...

0

https://www.quora.com/Why-does-the-United-States-of-America-use-110-60hz-power-and-why-does-India-use-230-50hz-power Synchronous clocks rely on the 50 or 60 Hz utility frequency of the AC electric power grid as a timing source, by driving the clock gears with a synchronous motor. They essentially count cycles of the power supply. While the actual frequency ...

1

The disadvantage of having too low a frequency is that the mains transformers become very large. However there have been lower frequency standards (25 Hz, 15, ect.) These are used by trains (mostly legacy systems).

1

Practical reasons include the skin effect (you do not want your frequency to exceed at most a few KHz by much unless you are willing to use something akin to Litz wire to transfer large currents) and the size of magnetic cores for transformers, which must be able to magnetically store more than the maximum energy to be transmitted in each cycle, such that ...

10

The two other answers address the frequency issue. The voltage issue is much simpler. If the voltage is too high, you run the risk of arcs between conductors. The minimum distance between conductors before an arc appears is proportional to voltage. At 240V, you arc at a distance of a few millimeters in air, depending on humidity. More voltage gets clearly ...

18

In the end, the choice of a single specific number comes from the necessity to standardize. However, we can make some physical observations to understand why that final choice had to fall in a certain range. Frequency Why a standard? First of all, why do we even need a standard? Can't individual appliances convert the incoming electricity to whatever ...

83

Why is mains frequency 50Hz and not 500 or 5? Engine efficiency, rotational stress, flicker, the skin effect, and the limitations of 19th century material engineering. 50Hz corresponds to 3000 RPM. That range is a convenient, efficient speed for the steam turbine engines which power most generators and thus avoids a lot of extra gearing. 3000 RPM is ...

1

It's human physiology based and I am not aware of any easily implementable numerical correction. The relationship is not linear or anyhow nice. The keyword for you would be equal-loudness contour. Read more about that. Actually, if you do e.g. psychoacoustical listening tests for timbre perception, the samples are adjusted to the same "psychological ...

0

The basic idea involved here is this: EM radiation of a pure, single wavelength of, say, λ=0.225nm is an infinitely long wave that lasts from a time of negative infinity to positive infinity. If you Fourier analyze such an infinitely long wave, the wave breaks down to just a wave with a wavelength of λ=0.225nm and zero contribution from waves of all other ...

1

No, it will rotate at a speed determined by the load. Witness that the current in, and thus the magnetic field produced by the stator coils is either in-phase with or anti-phase with the rotor current, with the $\pi$-phase change triggered by the split ring commutator. So the torque in each half of the rotor's rotation will throb at twice the AC line ...

0

Possibly? I think you can use the equipartition theorem to tell you that the energy stored in each degree of freedom is the same (at least for everything that has $E\propto x^2)$ So you should be able to count up all the spring modes, $m$ and then if there are $n$ atoms in your molecule the time average of your spring energy would be $\frac{m}{n}KE$ where ...

1

The connection of frequency to energy comes when one considers the covariant formulation of the electromagnetic wave propagation. In Panofski and Philips "classical electricity and magnetism" second edition chapter 21. This quote in particular. This associates a zero mass particle with a fourvector, i.e. energy and momentum . Text goes on to explain ...

0

it seems to me indeed strange that electrons get more energy by a higher frequency Why is it the high-frequency part that bothers you? Classically, high frequencies imply more energy. An example you might consider is whacking a ball-- the faster it spins, the higher it's frequency and the more rotational energy it has. More relevant, high frequency ...

0

As someone working in the field I recommend to start with The physics of musical instruments by Rossing and Flectcher. There is also an extension called The non-linear physics of musical instruments. I also recommend Cremer's The physics of the violin, and Mechanics of Musical In- struments edited by A. Hirschberg, J. Kergomard, and G. Weinreich. For futher ...

2

Screening means that from the view of the electron for which this is being calculated, the effect of the nuclear charge is lessened due to the other electrons which are orbiting the nucleus. In the first case, the K-shell electron is in the $1s$ orbital(which is spherically symmetric around the nucleus, and so it can effectively screen the nuclear charge ...

0

From Wikipedia: The hertz (symbol Hz) is the unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. In English, "hertz" is also used as the plural form. As an SI unit, Hz can be ...

Top 50 recent answers are included