Electric current. Sources of current
Electric current is the ordered (directed) motion of charged particles. In metals free electrons move, in solutions ions, in gases ions and electrons. To obtain a current a current source is needed: it separates charges and drives them around the circuit. In 1800 the Italian scientist Alessandro Volta built the first steady current source — the “voltaic pile” (zinc and copper plates with cloth soaked in salt water between them). A galvanic cell converts chemical energy into electrical energy (dry cells, “batteries”); an accumulator is charged and reused (phones, cars). A generator converts mechanical energy into electrical energy: in power stations it is driven by heat, water or wind. A solar cell converts light energy into electrical energy. The direction of current is conventionally taken from the positive terminal of the source to the negative. Electric current has heating, magnetic and chemical effects, and its effect on the body is dangerous: do not touch a socket without an adult.
“List of current sources”: groups list current sources at home and school and sort them into “battery”, “accumulator”, “generator” or “mains”. Safety: do not touch sockets, bare wires or damaged batteries; do not put a battery in the mouth or throw it in a fire, and keep small batteries away from small children.