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2answers
11k 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 ...
2
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2answers
114 views

Can work hardening of a metal be avoided?

My left earbud recently broke mid-wire: the bit that I like to fiddle with and bend. I fixed it, but I was wondering whether there are metals that don't work harden, or resistant to it? Is there a ...
2
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1answer
71 views

How is spring steel so hard?

The mechanical properties of a steel object are influenced by the metal composition, the manufacturing process, and the final heat treatment of the object. Spring steel is a steel that was heat ...
2
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1answer
117 views

Cold welding of a metallic surface

I have heard of cold welding, it's said that it's only possible if the surface is very clean. Can cold welding be accomplished by shearing a metal object and then immediately touching the newly ...
2
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1answer
76 views

The outside of a steel teapot is hot to touch. Does this mean that the water inside is necessarily at least as hot?

Some teapots, like this one Are made from thin steel which conducts the heat of the teapot quite well, meaning that you can't comfortable hold the sides while they're full of hot water. Tonight I ...
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1answer
81 views

How to calculate the speed of electrons in a metal

According to the Sommerfeld model, the electrons on the Fermi level has the relation $$ \epsilon_F=\frac{\hbar^2k_F^2}{2m_e}=\frac{1}{2}m_ev_F^2 $$ i.e. $\hbar k_F=m_ev_F$ with $k_F=(3\pi^2n)^{1/3}$ ...
2
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1answer
91 views

Why does carbon alloy with iron specifically?

Everyone knows what an alloy is: it's a metal made by melting two (or more) other metals together. Unless of course you're talking about steel. That's a metal made by mixing carbon (very much not a ...
2
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2answers
2k 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 ...
2
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1answer
113 views

Electron density in metals at non zero temperature

When computing the electron density in metals, the usual crude result is computed for zero temperature. That is, we integrate \begin{equation} n=\frac{8\sqrt{2}\pi m^{3/2}}{h^{3}} ...
2
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2answers
496 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 ...
2
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1answer
2k 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 ...
2
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2answers
3k 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 ...
2
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0answers
68 views

Can I use ultrasound to detect metal underground? [closed]

I am doing research which aim to detect metal underground. I know that most metal detectors are based on the concept of change of inductance of an inductor caused by mutual inductance with a ...
2
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0answers
94 views

Force constant of metals - Kohn anomaly

In Introduction to Solid State Physics (Kittel), it assumed the force constant between plane $s$ and $s+p$ $C_p=A\frac{\sin pk_0a}{pa}$ in metals to represent a Kohn anomaly. It says such a form is ...
2
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1answer
180 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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0answers
91 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 ...
2
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2answers
122 views

Is there any relation between temperature dependence of resistance and fermi energy in metals?

Given that the resistance varies linearly with temperature in metals, is there any way we can calculate the Fermi energy from this information?
2
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1answer
2k 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
350 views

Does Earth produce metallic elements in its core?

Does Earth produce metallic elements in its core?
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1answer
383 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
260 views

Why does room temperature water and metal feel almost as cool as each other?

From what I've read about heat, temperature and conductivity, I understand that the reason water at room temperature feels colder than most other things at the same temperature (like wood, air, ...
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1answer
11k views

Dielectric Constant or Permittivity of Metals

I'm wondering what the dielectric constant or permittivity of metals is --particularly copper. Do metals have an infinite permittivity?
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1answer
38 views

What determines the melting point

I have read that the melting temperature of a metal depends on the distance between atoms: The idea behind the theory was the observation that the average amplitude of thermal vibrations ...
1
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1answer
81 views

Can lightning actually weld fillings in your teeth?

So, I remember sometime in my childhood, someone was teaching me about lightning safety, and they explained that it was important to crouch low but keep as little contact with the ground as possible, ...
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1answer
98 views

Why does Ohm's law ignore the Lorentz force?

For example, the usual derivation of the complex dielectric constant of metals (using the Drude model) makes use of the Ohm's law in the Maxwell's equations, but what is never mentioned is why they ...
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1answer
48 views

Why metals fused in vacuum? [duplicate]

On Earth when two pieces of metal comes into direct contact with each other, nothing amazing happens. In a complete vacuum condition the two metals fused permanently, how and why?
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3answers
170 views

Is there any material that is NOT conductive and IS magnetically attractive?

Is there any material which is NOT conductive and IS magnetically attractive? I am in need of a material which I can shape and use within a machine. It must be very attracted to magnets similarly to ...
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1answer
142 views

Can metal rods detect underground wires?

Until not long ago, I was working in the drilling and infrastructure business. Some people I was working with used metal rods as a "quick and dirty" method of detecting underground wiring, before ...
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4answers
122 views

Measuring electric conductivity

My daughter is doing a science experiment on which metal (e.g., copper, silver, aluminum, iron) has maximum electric conductivity. We are assuming we can accomplish this by using different metal, 3 to ...
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1answer
404 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 ...
1
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1answer
96 views

What actually happens when electrons 'collide' with other electrons in a conductor to produce heat in an electrical circuit?

Textbooks describe resistance as involving electrons colliding with other ions in metals, resulting in a heating effect, though how exactly is this achieved? Although I am not required to learn the ...
1
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1answer
198 views

Grain boundary sliding in creep

To prevent grain boundary sliding so that creep is less likely to occur, usually engineers would design components of larger grains or have columnar grain structure to prevent grain-boundary sliding. ...
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1answer
136 views

How does the color of fine dispersed metal particles change between silver and black?

Small dispersed particles of metals are often black, while a solid object of the same material would be some shade of silver. The most notable example is the use of metallic silver as the black color ...
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1answer
261 views

What happens when molten metal cools within a strong magnetic field?

What happens when molten metal cools within a strong magnetic field? I don't know what more say, don't remember anything relevant to this in my uni text books.
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1answer
174 views

Semiclassical description of EM waves reflection from metallic surfaces

Imagine an EM wave impinging on a metal. Fresnel's formulas tell us that no wave can propagate through the metal, or that the transmitted field is an evascent wave with some penetration depth ...
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1answer
379 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 ...
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0answers
22 views

Why don't HCP metals have a brittle-to-ductile temperature transition?

I thought it had to do with the amount of slip systems...because BCC doesn't have as many slip planes, it cracks at low temperatures, while FCC has enough slip planes that it is not dependent upon ...
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0answers
31 views

Lindhard function for surface plasmon

Is there anybody that knows how to calculate the Lindhard function for the surface plasmon (between the surface of two metals of different dielectrics)? What I'm looking for is to find this function ...
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0answers
24 views

Does illuminating a conductor with light energy less than its workfunction change the measured conductivity?

For example, does the light absorbed in an exposed metal wire increase the average velocity of the electrons, hence increasing mobility and conductance?
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0answers
126 views

How can colors from heat tinting depend on temperature only?

Colors caused by heat tinting of a material can be listed by temperature. For example, for carbon steel: ...
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0answers
40 views

Any liquid metallic alloys which are safe to handle with bare hands?

http://en.wikipedia.org/wiki/Liquid_metal describes some alloys which are liquid at room temperature containing gallium, and sodium-potassium. We are advised not to handle them, and mercury, with ...
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0answers
156 views

How did gunsmiths create revolver cylinders in 1850's without the use of electrical drill? [closed]

How did gunsmiths create revolver cylinders holes in 1850's without the use of electrical drill? Which referces/ books specialize providing knowledge in similar molding method?
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0answers
59 views

Why do (most) metals cause problems in a microwave oven? Which metals (if any) don't? [duplicate]

Most of us have seen microwave ovens with metal racks or shelves, which challenges the common notion that you can't (safely) put metal in a microwave oven. What's going on here? Is it a matter of ...
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0answers
78 views

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 ...
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2answers
217 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 ...
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2answers
201 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 : ...
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0answers
372 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. ...
0
votes
2answers
2k views

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

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 ...
0
votes
1answer
49 views

When metal solidified, why is its surface not flat like polished?

I expect that what one can see on the outside of a just solidified piece of metal is just the "raw" surface of the inner stucture. Solidifying metals or alloys arranges in partial christal latices ...
0
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1answer
53 views

Electrical conductivity of metals on heating

What effect does heating have on metals (to be specific, on the electrical conductivity) ? And why does it have that effect?