In later pictures, amber dots show current, the flow of electricity. Here each blue dot is one electron.
Each atom's center is drawn as one red ball. The number on it is how many protons it holds, such as +29 for copper. The faint ring around it stands for the electrons the atom holds tight.
A loose electron is one its atom does not hold tight. Silver, copper, and gold each give one loose electron per atom. Aluminum gives three.
How well a metal conducts depends on two things multiplied together. One is how many loose electrons fit in a space. The other is how long each one goes between bumps.
The faint blue lines show where each loose electron went in the last second or so. A straight line is a trip between bumps.
Electrons do not really bounce off atoms like balls. The bump is a simple model of what slows them down.
The shaking is drawn far bigger than real. The extra shaking from heat is drawn bigger too.
Bumps turn some of the electrons' motion into heat. That is why a wire carrying current gets warm.
The lamp sets the current, so every bar carries the same current. The drift toward the positive end is drawn far faster than real. With the same current, aluminum's electrons drift slowest, because more of them share the same current.
Electrons move from negative to positive. Later pictures draw current the other way, from positive to negative. Both describe the same current.
Silver conducts best of all metals, but it costs far more than copper. Building wire is copper or aluminum, not silver, for that reason. Aluminum is lighter and cheaper than copper. Aluminum wire is made bigger than copper wire to carry the same current.
Gold is plated on some contacts because it does not tarnish. It does not conduct better than copper.
Aluminum made for wire is not quite pure, and some is an alloy, a mix with a little of other metals. Its standard says it must conduct at least 61 percent as well as standard copper wire. The pure aluminum shown here conducts a little better.
Water freezes at 32 °F (0 °C). Room temperature here is 68 °F (20 °C). Water boils at 212 °F (100 °C). Metal at 212 °F does not glow. The tint on the bar only marks the temperature.
The bar is heated or cooled from outside. Half an amp barely warms a bar this thick. On a job, a wire too hot to touch means something is wrong, so find out why.
The numbers use handbook resistance figures for pure metals and a simple model of loose electrons. The handbook does not list 212 °F, so those figures are worked out between the temperatures it does list.
The rings are a simple model of an atom. Real electrons do not travel in neat circles. The drawing is not to scale. The center of a real atom is far smaller than drawn.
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Loose electrons per atom1
Bumps a second, per electron40 trillion
Conducts, compared with copper at 68 °FConducts, against copper100%