Point at or tap any part to see its name. Tap the switch to turn it on or off.
In later pictures, amber dots show current, the flow of electricity. Here each blue dot is one electron.
Charge is what makes tiny bits push or pull on each other. Electrons are negative. Protons are positive. Each center is drawn as one red ball. The number on it is how many protons it holds, such as +29 for copper. The center also holds neutrons, which have no charge.
The rings, also called shells, 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.
Electrons move from negative to positive. Later pictures draw current going the other way, from positive to negative. Both describe the same current.
The motion is drawn so you can follow it. Real loose electrons dart around far faster than drawn. Their drift from the battery is far slower, less than a thousandth of a millimeter per second in this bar. A thin wire carrying the same current has a faster drift, because the current squeezes through less room.
A conductor is a material current flows through easily. An insulator lets almost no current through. One to three outer electrons usually means a conductor. A full or nearly full outer ring usually means an insulator. Four is in between. This rule of thumb has exceptions. It is for pure elements, not for compounds like plastic.
Copper and silver each give one loose electron per atom. Aluminum gives three. Silver conducts best of all metals, but it costs far more, so most building wire is copper. Aluminum wire must be bigger than copper to carry the same current.
More loose electrons per atom does not mean a better conductor. Aluminum has three per atom, but it carries current less well than copper.
Each bond in silicon holds two electrons, one from each atom. So each atom's four outer electrons sit in four bonds.
The silicon is pure and at room temperature. Silicon is called a semiconductor. A tiny trace of another element makes it conduct far better. Computer chips are made that way.
Enough voltage, heat, or damage will push current through plastic. That is why damaged insulation is dangerous.
The plastic is polyethylene, used in some wire insulation. It is long chains of carbon and hydrogen, so it has no single outer ring count. Each line between atoms is a bond holding two shared electrons. The readout says "In bonds" for that reason.
The battery is a 6 volt lantern battery. The lamp is a 6 volt, 3 watt lamp, 12 ohms when lit. The bar is 4 inches long and 1/2 inch square.
The current uses typical handbook resistance figures for each material at room temperature. Pure silicon and plastic change a lot with purity, heat, and moisture. Plastic lets through so little current that no meter can read it here.