40 votes
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Is it possible to generate light with an antenna?

Photonics is a thing, and it very much treats light as electromagnetic waves in waveguides on silicon, with mixers, delay lines, matching circuits, amplifiers etc as you'd do for a RFIC. Just as an ...
Marcus Müller's user avatar
23 votes

How can a DC spark create EM waves?

The spark, unless it is a continuous steady arc, will fluctuate in intensity. This means it will have an AC component even if the current never goes in reverse. In practice sparks are very noisy and ...
Transistor's user avatar
  • 175k
22 votes
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Do square wave exist?

As you know (since you mentioned the Fourier transform), a square wave can be represented (well, almost -- see below) as the sum of an infinite series of sine waves. But it would not be possible to ...
Glenn Willen's user avatar
  • 2,286
20 votes
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In which direction do electric signals flow?

If electric signals are the propagation of EM waves at close to c in which direction do these waves travel? In the conventional direction? In the direction of electron flow? In both directions? "...
pjc50's user avatar
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17 votes
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What makes E-bomb or Electromagnetic pulse (EMP) destructive?

The reason such a pulse is so destructive is because it has a broad frequency range, and can therefore affect things with a wide range of physical dimensions, and the large amplitude of the pulse. ...
Olin Lathrop's user avatar
17 votes
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Bad effects of coiling electrical cables

In the article that you linked to, it says in one of the answers, The most notorious feature of loaded coiled cables is that they potentially generate a lot of heat in a tight space. In most cases ...
i0oklng 1lke c0nfus10n's user avatar
17 votes

Is it possible to generate light with an antenna?

The wavelength of 750 THz is 400 nm so, your dipole would need to be 200 nm long to make a radiating antenna but your biggest problem (in 2021 and probably beyond) is being able to produce a frequency ...
Andy aka's user avatar
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16 votes
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Does Shielding "Electrically" shield "Magnetically" too?

You would not be alone in this one. This is an often misunderstood phenomenon. Static magnetic fields can not be shielded. They can be re-directed using ferrous materials but even those will not ...
Trevor_G's user avatar
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14 votes
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Are there types of standard coaxial cable with a propagation velocity of 0.9c? What would be the application?

Air lines still exist, with velocity factor very close to 1.0. These are AFAIK mainly used in old-fashioned VSWR measurements. The advantages are that the dielectric constant of air is fairly stable ...
The Photon's user avatar
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14 votes
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Why no macroscopic electrostatic electromechanical parts?

Have you calculated the voltages you'd need in order to get the equivalent force or torque? It's much easier to build compact machines of equivalent power based on high currents rather than high ...
Dave Tweed's user avatar
  • 172k
13 votes

When an electromagnetic relay is switched on, it shows a dip in the coil current for a millisecond but then increases again. why?

A relay coil is inductive, and the mechanical parts form part of the magnetic circuit. When the clapper moves after current is passed through the coil the magnetic circuit closes, changing the ...
Spehro Pefhany's user avatar
12 votes

What's wrong with my electromagnet

Steel bolts don't make good magnets. Soft iron is much better. With that low number of turns on the coil, you will have to put a LOT of current through it to get any strength out of it. You have to ...
JRE's user avatar
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12 votes
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How do I build an electromagnet?

I'm sorry, but you need to find a new project. Lifting a paper clip at 8 inches will require an extremely powerful magnet. If you still want to see what you can make, you need to change your wire ...
WhatRoughBeast's user avatar
11 votes

What makes E-bomb or Electromagnetic pulse (EMP) destructive?

Two things make an EMP weapon destructive: the tremendous amount of energy released the very short duration of time over which it's released Another smaller, but similar example is lightning. A ...
Phil Frost's user avatar
  • 57.2k
11 votes

In which direction do electric signals flow?

signals travel in all directions like waves in a pond, they are a disturbance in the current not necessarily a current themselves.
Jasen  Слава Україні's user avatar
10 votes

How do I find out if this mobile tower is bad for my health?

No, it would not be a good investment. The device you linked to is designed to detect power-line frequencies (50 Hz or 60 Hz). There are more advanced devices, but as the Amazon comments make clear, ...
Adam Haun's user avatar
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10 votes

Why can't you put a plane under a trace antenna?

An antenna converts a low impedance transmission line (from the chip or also via a coax or stripline) to a high impedance at the end of the antenna. The high impedance is to suit the impedance of free ...
Andy aka's user avatar
  • 451k
10 votes

Bad effects of coiling electrical cables

Is there any bad effects of coiling electrical cables ? That depends on the cirumstances. The electrician is correct for the part of electrical engineering that he (probably) deals with. And that is ...
Bimpelrekkie's user avatar
  • 80.8k
10 votes

How can a DC spark create EM waves?

It is not the DC part itself. It is the raising edge. The spark creates a square-like waveform which actually consists of infinitely many sine waves. That is explained by the Fourier transformation. ...
tomas789's user avatar
  • 201
10 votes

Is it possible to generate light with an antenna?

The other answers are correct, the frequency of light (i.e., visible light) is so fast that it's really hard to do. People do make THz light (even longer wavelength than infrared) using antennas, and ...
KD9PDP's user avatar
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9 votes
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What are some quick, cheap hacks for determining the source of EMI in my house?

A yagi antenna and a cheap SDR might be good to play around with. Make sure the antenna and SDR work in the frequency range of interest (so if you want to look for wifi signals, then the antenna and ...
Voltage Spike's user avatar
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9 votes
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How can a DC spark create EM waves?

We usually use the math of sine waves ("AC") to analyze electromagnetic radiation, and there are good reasons for this. However, the first treatment of how charge generates radiation that my ...
John Doty's user avatar
  • 3,579
9 votes

How do I build an electromagnet?

Here's an example electromagnet you can buy: ELECALL electromagnet. The datasheet shows that the most powerful model (the ELE-P100/40) can run at 12 volts at 1 amp (12 Watts). The lifting force at ...
Xavier's user avatar
  • 191
9 votes

Why is it not standard practice to integrate the output of an antenna?

Most communication is done using signals that are sufficiently bandlimited that we simply don't have any reason to care. The derivative of the signal is the same thing as the signal, except for a term ...
hobbs's user avatar
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9 votes
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Spending money on gold cables

For low level signal connections, it can be useful to have connectors plated with materials that either don't oxidize (gold) or have an oxide which is conductive (silver). For the same reason you can ...
bobflux's user avatar
  • 74.8k
9 votes

When an electromagnetic relay is switched on, it shows a dip in the coil current for a millisecond but then increases again. why?

Welcome to EE.SE. The relay armature was closed for the first 25 ms (when the control circuit was on... The power is on for the first 25 ms but the armature won't close instantaneously. As the ...
Graham Nye's user avatar
  • 4,142
9 votes
Accepted

Would reducing the air gap between the rotor and stator to micrometer/nanometer scale distance proportionately increase a motor's power?

For a constant field in the gap, the motor armature and running characteristics are independent of the size of the gap. However, to get that constant field, a wound motor needs excitation current more ...
Neil_UK's user avatar
  • 165k
8 votes

Does a twisted pair cable radiate more EM radiation than non-twisted pair?

Yes, it is vice-versa, through the principle of reciprocity. Any "antenna" is just as (in)effective at transmitting as it is at receiving, so the advantages of twisting the conductors together apply ...
Dave Tweed's user avatar
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