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0answers
31 views

advantages/disadvantages of a cylindrical microwave oven cavity in comparison to a rectangular cavity

Why are rectangular cavities preferred for standard microwave ovens with a frequency of 2.45 Ghz? What is the reason that you can hardly find a circular cavity? What are the disadvantages of ...
36
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4answers
5k views

How to imagine WiFi signal propagation?

When thinking about how the WiFi signal propagates through a household, can I use the following thought experiment? Assume absolute darkness. Place a strong lightbulb where the WiFi access point ...
7
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0answers
87 views

Why is it that fractal antennas can filter out so many frequencies?

As known, fractal antennas are used for example in cell phones. But why is it that so many different kinds of frequencies can be filtered out of the forest of radio waves surrounding us? Is it because ...
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0answers
16 views

Load matching in a transmission line [duplicate]

Can somebody explain me easily and clearly why when you want to transform a 50 ohm load impedance through a piece of transmission line in an arbitrary one let's say Z (complex number); that is exactly ...
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1answer
51 views

How to shield myself from the LTE radiation coming from my phone while working on my Laptop? [closed]

I am connecting to the internet with the tethering option on my phone. I wonder if there is a way to shield myself from the LTE radiation (Long-Term Evolution, commonly marketed as 4G) as I am exposed ...
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2answers
76 views

Is the CHAMP missile capable of doing what they say it does? [closed]

CHAMP, A new counter-electronics directed energy USAF weapon was created by Boeing Phantom Works with the intention to damage and / or destroy electronic target equipment without causing structural ...
0
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1answer
53 views

Is fire more harmful than a phone?

I have read somewhere that the higher the frequency of electromagnetic radiation, the higher the damage it causes to your body, and visible light has a very high frequency in comparison to microwave ...
0
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1answer
47 views

Cavity resonator modelling and simulation of em fields inside the cavity

I want to model a cylindrical cavity resonator and study the different modes of em fields inside it using MATLAB/COMSOL. Please refer me books/articles or other resources so that I can achieve my ...
5
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1answer
59 views

Why are magnetron apertures in home microwaves so small?

I'm curious why magnetrons from a home microwave like in the image below can have an aperture between the magnetron cavity and the waveguide that is significantly smaller (2-6mm usually) than the ...
0
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0answers
55 views

What can I put in my microwave oven that won't get warm?

I have a fuzzy understanding that microwaves heat food because the waves interact with polar molecules in the food, causing them to vibrate, and the vibrations are heat? Correct me if I'm wrong. To ...
-4
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1answer
104 views

Why does microwaved water kill plants? [closed]

I've read tons of articles about microwaved water klling plants and the most of them said it was a myth. So I decided to do this experiment myself on cress plants. I repeated the experiment three ...
0
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0answers
33 views

Phase noise measurement with an IQ mixer

I have a question regarding a measurement scheme of phase noise that I'm trying to implement. The idea is that I have two identical signal generators (I actually do) that generate a sinusoidal voltage ...
4
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1answer
210 views

Should I place a spoon in a cup of liquid before heating it in a mircowave?

Metal objects in microwave ovens are known to be somewhat dangerous. However, my microwave has the following label stuck inside: It seems to imply that this particular oven forbids heating drinks ...
0
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1answer
80 views

What do we mean by wavelength of any electromagnetic wave?

What do we mean by wavelength of EMW? Wavelength of oscillating electric field or the oscillating magnetic field? Or is it that both the electric and magnetic field waves have same wavelength? If ...
0
votes
1answer
26 views

Microwaving two products based on individual instructions

Suppose I have a cake, which has instructions to heat it for 60 seconds in the microwave. I also have some custard, which has instructions to heat it for 30 seconds in the microwave. For convenience, ...
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2answers
34 views

Electric fields with different frequencies, total intensity?

What happens when electric fields with different frequencies are combined? Is it possible to calculate the intensity of the total electric field? For a project, I need to simulate a brain treated ...
0
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0answers
24 views

Books on Spectral Jacobian

Can anyone point me a book to better understand "spectral Jacobian". I am studying X-parameters, I have the book X-Parameters: Characterization, Modeling, and Design of Nonlinear RF and Microwave ...
1
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0answers
59 views

Can I safely heat stainless steel 1-2 inch ball bearings in a consumer microwave? [closed]

I am looking to heat 1 or 2 inch stainless steel spherical ball bearings in a microwave. I would like the bearings to get to about 140 degrees F but not hotter. I have read that this should be fine as ...
0
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0answers
47 views

What are the properties of the electromagnetic radiation from a magnetron?

There are different modes of EM radiation. A bulb emits photons in a wide range of wavelengths and without polarisation. Radio waves are polarized modulated radiation. What is about the radiation ...
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0answers
132 views

Loaded Quality Factor

I came up with an expression for the reflected power of a resonator: $$\left| \Gamma \right|^2 = 1 - \frac{1-\left(\frac{\kappa - 1}{\kappa + 1}\right)^2}{1 + 4 \left( \frac{Q_U}{(\kappa + 1)} ...
1
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0answers
34 views

Microwave Farraday cage shielding

After a decade of using a microwave oven in my house I figured out I never cared to connect the grounding cable. So my question is regardless of electrical shock risk, does the Microwave Faraday cage ...
0
votes
1answer
70 views

Dodging Microwaves [closed]

I'm not sure if I'm just being paranoid or not but I'd like some explanation as to whether my fears are justified or not. With a normal microwave oven you can usually end the cycle early by opening ...
0
votes
0answers
57 views

What is the effective volume for TE011 mode in a cylindrical cavity?

Is the effective volume same as the volume of the cavity? I am not sure I understand the concept of effective volume.
1
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1answer
87 views

Light / TEM wave in a hollow waveguide

I'm cramming for my EMF exam, and a question came up: Light in free space is an example for a TEM wave, isn't it? (Maybe thats already my mistake) And we learned that in a hollow waveguide only TE ...
2
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0answers
25 views

In theory, Is it possible irradiate a blob of matter -for instance- with microwaves in order to that matter emit more energy than has received?

Suppose that you want coerce a block of matter to lose his energy. I mean thermal energy. This should be done by irradiation of more energy. The final thermal energy should be lower that the original ...
3
votes
1answer
557 views

If a microwave oven disk rotates to warm up food, why doesn't it go up/down/sideways?

This has been in my mind for a while... Well, actually everytime I heat any food with a greater amount of liquid in it: a microwave oven warms up food by inducing polar molecules in the food to ...
1
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1answer
59 views

Shape of metal to be heated in consumer microvave oven? [closed]

I tried to use a common 900 W microwave oven melt some alloy with low melting point (138 deg C, eutectic bismut/tin). The metal did not heat up, neither did the metal container, which makes me think ...
0
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1answer
135 views

Distance of electromagnetic waves based on frequency

I would like to ask your opinion regarding this matter: Based on the relation of frequency and wavelengths, the higher the frequency, the shorter the wavelengths and therefore the distance of travel ...
2
votes
2answers
373 views

Why does aluminium foil spark in the microwave? [duplicate]

I don't understand fully why aluminium foil sparks in a microwave oven? I think what is happening is the oven sets up an electric field, and the field induces a current in the foil (how?), and ...
0
votes
1answer
257 views

Electromagnetic cooling

Heat means stored kinetic energy in matter. Microwave owens and induction heaters works on increasing kinetic energy on matter. Is it possible to make inverse of this heaters like cooler. Can we ...
2
votes
0answers
281 views

Can a microwave oven induce an accumulation of static charge in food?

I often "touch test" microwaved food to see if it is heated up enough to my preference. In doing so, I sometimes notice the characteristic tingle of a static discharge between the food and my finger ...
3
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0answers
66 views

Why do rings form on microwaved CD/DVDs?

Here's a microwaved CD. As you can see, the disc has been destroyed, but there are very clear circular rings bridged with lines. Why are rings formed when microwaving discs?
7
votes
1answer
1k views

Why when I put a teabag into microwaved water does the water fizz? [duplicate]

When I am in a rush, I will heat up water in a cup in the microwave for tea. I usually put the cup on high for 2 mins. When I put the teabag in, the water starts to fizz almost like it is ...
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2answers
254 views

Does a source emitting visible light also emit infrared, microwave and radio waves?

I have a bulb which is hot enough to emit visible light and obviously it's hot enough to emit radiation which lies before the visible light temperature i.e. radio waves, microwaves, and infrared ...
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2answers
4k views

Why do we use microwaves in microwave oven?

We know that any object above absolute zero emits electromagnetic radiation. So hotter the object shorter the wavelengths. In the electromagnetic radiation spectrum radio waves has the longest then ...
2
votes
1answer
49 views

How come a current sheet of $J_s = J_0 \hat{x}$ produces plane wave solution?

Given in the picture. There is a current sheet $J_s = J_0 \hat{x}$. Supposedly Jo is not oscillating. So, how does this thing create a plane waves propagating away from the current sheet? Shouldn't ...
5
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3answers
3k views

Why do microwave ovens use radiation with such long wavelength?

According to Wikipedia: Consumer ovens usually use 2.45 gigahertz (GHz)—a wavelength of 12.2 centimetres (4.80 in). Typically, I put the dish inside the oven in its center. I suspect most ...
2
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1answer
151 views

Does humidity affect passage of microwaves?

Does the humidity level in air affect the passage of microwaves? I've heard people say water is radio opaque, so could a high humidity level lead to faster signal degradation? As an example, would ...
0
votes
1answer
43 views

Energy variations of cosmic background radiation

Has anyone been able to measure a difference in the energy density of Cosmic Background Radiation in a gravity well compared to zero gravity?
4
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2answers
121 views

Microwave oven and heating my sons milk

I heat up my sons milk in the microwave... I use the same volume all the time and always punch in 42 seconds (on high) and his milk comes out the perfect temp every time. However, sometimes he ...
0
votes
1answer
166 views

Why would a sweeping LIDAR or RADAR beam not produce an artificial Doppler shift?

Assuming a bi-static Radar or LIDAR with a stationary transmitter and a stationary target and a stationary receiver, with a sweeping RADAR/LIDAR beam reflecting off a stationary target: Why would the ...
0
votes
1answer
76 views

Dielectric heating - does EM field transfer energy to polar molecules?

In AC field, polar molecule are trying to align with external field. At high freguencies, changes of field are so quict, that molecules cannot align with it. This leads to increasing kinetic energy of ...
12
votes
3answers
502 views

Is it really possible to “discover” the speed of light with a microwave oven?

I've seen a number of sites/videos online that describe a method for measuring the speed of light, using a microwave oven and a chocolate bar. For example, this video on youtube. The basic idea is to ...
1
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0answers
64 views

I need to remove water from a system [closed]

I work in an industry and I need to remove water from a system. The scenario: There is a washer and a blower on a conveyor belt. The item being washed is plastic (not sure what type) and can't be ...
0
votes
1answer
197 views

Why does plastic wrap grow, then shrink, then grow again when microwaved?

The other night I was reheating a bowl of leftovers in the microwave. There was a fair amount of liquid in the bowl, so I covered the bowl with plastic wrap when I put it in the microwave. When I put ...
19
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2answers
5k views

How do microwaves heat moisture-free items?

Today I learnt that microwaves heat food by blasting electromagnetic waves through the water molecules found in the food. Does that mean food with 0% moisture (if such a thing exists - dried spices?) ...
2
votes
2answers
575 views

What would a graph of temperature increase of a cup of water in a microwave look like?

My lunch had been in the microwave for a minute or so, and I was wondering if I took it out 10 seconds early, would the amount of temperature it increased in that 10 seconds be more significant, less ...
0
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1answer
131 views

If halving signal strength is only a 3db drop, why can't cell phones be much lower powered?

My phone can receive a signal that's -90dBm. That's roughly one-billionth of a milliwatt. Cutting a signal's strength in half only drops the signal by 3dBm. Apart from slightly higher range, is there ...
1
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3answers
821 views

2.4Ghz microwaves have a 12cm wavelength. How do microwave ovens leak radiation, since any gap in the shielding is much smaller than that wavelength?

I've read (I think on wikipedia, but I can't find the reference) that microwave oven leakage is often due to faulty seals on the door. Given that any gap in the door is going to be far smaller than ...
3
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2answers
2k views

Will a microwave heat sand?

I want to cook Turkish coffee on heated sand at school. I have difficulty accessing some easier method of heating, so I was going to try to heat sand in a microwave. It was then pointed out to me that ...