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0answers
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Maximise magnetic force at one point while minimizing at another

Is it possible to have a magnet that attracts one object strongly, but not another object behind that first object? Given an (electro-) magnet M above two thin parallel steel sheets P1 and P2 in the ...
3
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1answer
917 views

Why do most metals appear silver in color with gold being an exception from a scattering and EM viewpoint?

Related: Why are most metals gray/silver? After reading Johannes’ impressive answer to Ali Abbasinasab question of why do most metals appear silver in color with the exception of gold (and copper), ...
3
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1answer
1k views

What causes stress concentration (aka stress risers/raisers) at corners?

I've read a few explanations about why stress concentration occurs at sharp corners but I don't find the explanations intuitive. Can anyone explain it perhaps using an analogy such as atoms "holding ...
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6answers
7k views

Why are most metals gray/silver?

Why do most metals (iron, tin, aluminum, lead, zinc, tungsten, nickel, etc.) appear silver or gray in color? (What atomic characteristics determine the color?) What makes copper and gold have ...
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1answer
241 views

Why aren't superconductors shiny? [duplicate]

Superconductors are really good at conducting electricity. Should they not reflect light very well too?
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0answers
98 views

Is this a correct description of bonding in a metal?

I am reading the paper "Twenty five years of Finnis-Sinclair potentials" by Graeme Ackland, Adrian Sutton, and Vasek Vitek, Philosophical Magazine 2009, 89, 3111-3116. It is a review-type article ...
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2answers
401 views

How would a change in ambient temp affect a radiator?

I'm curious if you have a radiator or say a block of metal (lets say it's copper since it has the highest thermal conductivity) and on one side is a processor producing heat. At idle the processor ...
6
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1answer
162 views

Reflectivity of a glowing-hot metal surface

When a polished piece of metal (or steel in particular) is heated to incandescence, how do its reflective properties change? Given a mirror-like surface, would the object temporarily cease to act ...
3
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1answer
190 views

Why do cold metal plate make less noise?

I have a metal gate in my home so I have noticed that when it is a hot day and if I hit it it makes a lot of noise but when there is a rainy day and the weather and the gate re cold and if I hit the ...
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2answers
285 views

Does Earth produce metallic elements in its core?

Does Earth produce metallic elements in its core?
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1answer
1k views

How long does it take a warm object to cool in air?

This is a work-related question. A warm steel torus of a given diameter & thickness is left in a room held at a controlled temperature, how long does it take to reach equilibrium? Assume the air ...
20
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3answers
8k views

Is there a compound denser than the densest element?

I'm musing about how to give students an intuitive feeling about density by letting them lift a same sized volume of different materials, e.g. 1 liter of water, a 10x10x10 cm cube of iron, lead etc. ...
3
votes
1answer
64 views

Resources in space, and their distribution

I'm making a video game in which the economics of an interstellar civilization is important. What I'm wondering is, how are resources in space distributed? Since everything ultimately comes from ...
3
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2answers
349 views

X-ray diffraction from Metals

Is X-ray crystallography is possible for metals? Or not due to absorption?
3
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4answers
2k views

How does positive charge spread out in conductors?

I know that when there are excess positive charges in a conductor, for example, a metal sphere, the positive charges will spread out over its surface. However, I am confused about how this excess ...
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1answer
1k views

Resistance between two points in an infinite metal sphere/cube

Let's imagine that we have a tridimensional metal object of infinite size, and decide to calculate the resistance between two arbitrary points. How would we go about doing this? I have thought of two ...
1
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2answers
169 views

Is it possible to reduce the sound, when two metal objects collide (perhaps with some coating) without reducing the rigidity of the surface?

I have a system, where there are ball bearings on the pistons that clamp the metal plate with special dents for ball bearings. The system should be precise, because it is used for microscopy. It also ...
4
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1answer
309 views

Impurity scattering temperature dependence

Is there any temperature dependence of relaxation time in impurity scattering of conducting electrons? It seems to me that there is none. But, some people claim that there is. So if you could ...
2
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0answers
85 views

Are metal modes mixed with molecular modes during surface enhanced Raman effect?

This question is dedicated to Martin Fleischmann (1927-2012). When a molecule is adsorbed on a metal surface, the Raman scattering amplitude from the molecule is enhanced. According to Wikipedia, the ...
4
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1answer
78 views

materials that repel positrons?

In this article is discussed at some length positron formation in metallic surfaces. Positrons have work functions that describe how much energy they have to receive in order to be extracted from the ...
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2answers
1k views

What characterizes a metallic sound, and why do metals have a metallic sound?

We know that when we strike a metal, it usually has a characteristic "sharp" sound, unlike when we strike wood, say. What characterizes this "metallic sound"? Does it have a well-defined power ...
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2answers
186 views

Why energy saving light bulbs contain rare earth?

Reading a french article talking about a recycling unit of rare earth from energy saving light bulbs near Lyon - France (here is the official press release of the Salvay company), I was wondering : ...
0
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1answer
329 views

Why do electrons make a Fermi sphere?

In Sommerfeld theory for metals, after determining all of the possible levels for a single electron, one says that we build up a state for a system with $N$ electrons by filling up those levels, ...
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2answers
1k views

What is the best material and design for building a parabolic dish?

I'm currently using a homemade metallic spaghetti strainer with a wifi adapter inside it to increase my wifi adapter's signal reception, but would think that a different material, like the aluminum ...
1
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1answer
332 views

Euler's buckling formula applicable for impact calculations?

$$F = \frac{\pi^2 EI}{(KL)^2}$$ Is Euler's buckling formula applicable for impact calculations, considering speeds relevant for a car or aircraft crash? If there is a level where the formula ...
1
vote
1answer
333 views

Formation of the overlap in metal electron bands

I understand that metals have overlapping of valence and conduction bands. But is this because there exists a partial conduction band within the top part of a metal valence band, or because the ...
8
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1answer
141 views

Third-order susceptibilities of metals?

Can anyone point me to a source for measurements of the third-order nonlinear electric susceptibilities $\chi^{(3)}$ of various metals? Specifically in relation to the AC Kerr effect, so measurements ...
4
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4answers
7k views

In electrostatics, why the conductor is an equipotential surface?

Since the electric field inside a conductor is zero that means the potential is constant inside a conductor, which means the "inside" of a conductor is an equipotential region. Why books conclude ...
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3answers
17k views

In electrostatics, why the electric field inside a conductor is zero?

In electromagnetism books, such as Griffiths or the like, when they talk about the properties of conductors in case of electrostatics they say that the electric field inside a conductor is zero. I ...
3
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2answers
4k views

Will the hole on a metal disc expand or contract upon heating? [duplicate]

Possible Duplicate: Will a hole cut into a metal disk expand or shrink when the disc is heated? The metal disc of diameter D1 has a hole in it and the diameter of the hole is D2 (D2 Now, ...
3
votes
2answers
9k views

Are all metals good conductor of electricity?

I am writing an article for kids, which is on conductors and insulators of electricity. If I make a statement that "All metals are electrical conductors and all non-metals are electrical insulators" ...
2
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2answers
1k views

Properties to select suitable materials for making permanent magnets

I have read that soft iron is suitable for making a permanent magnet. Because it is required for permanent magnet to have high coercivity and high retentivity. Same text also said earlier that soft ...
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0answers
302 views

Electrical machines: electrical and mechanical properties of steels and cast iron

I would like to know a good source of information for the common metals (steels and cast iron). Information that I need are basically the mass density and the electrical conductivity or resistivity. ...
4
votes
1answer
2k views

What tests can I do at home to identify any metal?

Regarding a question on another Stack Exchange site which identifies a weighted Lego brick to be some kind of metal, I wanted to know how to identify a metal, perhaps limited to household objects like ...
2
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2answers
7k views

How do metallic objects interfere with X-Rays?

During my visit to the doctors', I recollect having seen the sign which says Please remove all metallic objects from the body before the commencement of the X-Ray How do metallic objects ...
6
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1answer
1k views

What is the penetration length of static electric field into conducting metals?

How large is the penetration length for static electric field into good conductors? I have two versions: (1) few atomic spacings $$a\sim n_{e}^{-1/3},$$ and (2) Debye length computed by Fermi ...
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3answers
19k views

Hollow Tube Stronger than Solid bar of same Outside Diameter (O.D.)?

I was listening to some co-workers talking about problems meeting stiffness requirements. Someone said that even with a solid metal rod (instead of the existing tube) we could not meet stiffness ...
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8answers
28k views

Will a hole cut into a metal disk expand or shrink when the disc is heated?

Suppose you take a metal disc and cut a small, circular hole in the center. When you heat the whole thing, will the hole's diameter increase or decrease? and why?
4
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2answers
104 views

Metal Dilemma: Only very few civilizations per galaxy

This is a question in the area of extraterrestrial life. While life may be possible without it, space travel is probably impossible without metal. Metal is created in stars and heavy metals (above ...
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1answer
1k views

What makes some aluminium alloys so strong while remaining light?

Compared to cast iron, for example, certain alloys of aluminum have both strength and weight advantages. How can aluminum be so strong while being so light?
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2answers
674 views

If sound wave is going to hit any metals can it make that metal electrons into exited state?

What will happen when sound wave hits the metals with very high frequency can it make the electrons to exited state. If it happens then what will be the state of that metal
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2answers
2k views

Why is quicksilver (mercury) liquid at room temperature?

This is a nice question when you find it out, and I am really looking for a proper answer. Take quicksilver (Hg) in the periodic table. It has one proton more than Gold (melting point 1337.33 K), and ...