Transformers: Alternating current can be increased or decreased by a transformer. This allows us to transfer electrical energy at very high voltages and over hundreds of kilometres, without osing any of the energy as heat. Transformers consist of two windings made of copper wire. If we apply an alternating current to one of them, it will produce a certain voltage in the ther. Electromagnetic effects: He noticed that electricity could be generated by using a magnet and an electrical conductor. This principle allows us to build dynamos and alternators. Effects of electric current: Heat: the movement of electrons through an electrical cable is both slow and disorderly. The electrons often collide, increasing the temperature of the cable itself. Light: For example, we can heat a conductive filament or energise the electrons of a fluorescent gas. We can also use an electronic device called a light-emitting diode. Electromagnetic generators: Electromagnetic generators transform mechanical energy into electricity. There are two types of generators: dynamos and alternators. Dynamo: consist of a magnet and a rotary coil. The col is located between the two poles of the magnet. Alternator: is almost identical to a dynamo, except for th commutator. Electrical quantities: the amount of energy that a generator can transfer to electrons depends on its voltage or electric tension. This is measured in volts. Direct current: the electrons always flow in the same direction with the same current. Alternating current: the flow of electrons changes direction 50 times every second, as if the + and - poles of the socket were connstantly changing places. In addition, the electric current is not always the same.