Why do you need Alternate Current, when you can obviously solve almost all problems with Direct Current? So you could charge the high voltage battery of an electric car directly and would not need a converter from AC to DC. According to all previous experience, charging is also much faster.

Yes, but e.g. in an electric car we already reach a limit, because we cannot operate the motor directly with direct current. Any electric motor needs a DC/AC converter, at least in terms of its mode of operation. And we cannot generate direct current directly, a conversion process is always necessary. Only for storage, direct current is absolutely necessary.

Current is generated in a magnetic field, whereby it does not matter what it is generated by, e.g. permanent magnets such as the bicycle dynamo or electrically, such as the generator in the vehicle. The latter can be achieved with one or more current-carrying coil(s) that are permanently installed in the generator housing. Even if one carries out the simple experiment shown in the picture above, i.e. the electrical conductor only carries out a back and forth movement, an alternating current is already generated at its ends.

By the way, the first motorists did not yet have any generators available, although soon enough motor torque would have been left to drive them. Even before the electric lighting soon came on the scene, such an ignition was regarded as the measure of all things, and sometimes even had them retrofitted, e.g. by Bosch. But it also meant taking a battery with you and usually charging it in the house after every trip.

Of course, alternating current could not just be generated by alternating electrical conductors. A rotary motion had to be introduced into the magnetic field, which then required two carbon brushes on slip rings to bring the electrical energy from the rotating conductor to the outside. At the same time, the conductor was extended and wound into a coil to produce more electrical current per revolution.

The inner part of such a generator was called an armature, the type of power generation was attributed to so-called induction. This comes from Latin and means 'to lead into'. Thus one could better imagine the origin of the electrical energy in the wire. Very important for the electricity produced there is that it is time-dependent. And if we look at transformers, induction also works without visible movement.

If science wants to describe something, one should not expect a description. As a rule, the result is a mathematical equation. We are lucky here, because at least an additional curve is drawn, so that one can go on more easily seeing through.

What does the 'sinus' in this 'sinusoidal oscillation' mean, which one perhaps got to know in connection with triangles? In the picture below, a pointer of length U₀ should move on a circular path through all four quadrants. In the right-angled triangle, the sine is the ratio of the opposite cathets of the indicated angle to the hypotenuse formed by the rotating pointer.

In the first quadrant, this sine increases first strongly and then less and less. If it rotates through the quadrants 2, 3 and 4, it continues to exactly represent the curve shown above.

Here is the first equation:

U₀ is the maximum deflection, the amplitude. The rotation is uniform. ω is the rotational speed or angular frequency.

If T is the duration of a period, i.e. an oscillation in one direction and then in the other, then ω is the number of oscillations per second, because 2 π denotes a full circle, i.e. a complete oscillation. The unit for ω is 1/s, which strongly reminds of the engine speed, which is related to the minute. These are then all quantities, in order to determine the height of the tension after a certain time computationally.

Here we only consider the units of the equation above. U₀ is multiplied by a factor from -1 to +1.