Everyone heard that an alternating sinusoidal current flows in the conductors of household wiring. But for a person unfamiliar with electrical engineering, the terms "sinusoidal" and, especially, "variable", do not say anything. In this paper, we will try to give a general idea of this, which everyone can understand.
First of all, you need to determine what an electric current is. According to the existing explanation, a current is a directed movement of elementary particles with a positive or negative sign charge . Usually, electrons are understood as particles, but this is not entirely true. An atom that has lost an electron, due to the protons present in the nucleus, acquires a positive charge, becoming an ion. EMF acts not only on an electron, but also on it. Suffice it to recall that in the calculations the positive direction of the current is taken from plus to minus, although in reality, negatively charged particles move in the opposite direction.
Where do these particles come from? Imagine the structure of a conductor: a crystal lattice with atoms in nodes. Each atom can conditionally be described as a miniature solar system. In the center is a massive nucleus consisting of protons and neutrons, and electrons revolve around it in orbits.
The proton charge is positive, and the electron is negative, so they are mutually attracted. The closer to the core, the stronger this interaction. In order for a current to arise, it is necessary to free some of the electrons from the atoms and make them move in the right direction. In generators, this task is successfully performed by a rotating magnetic field. It communicates the missing energy to electrons in outer orbits, releasing them. Of course, there is no direct movement. We are talking about the exchange of these particles between the nearest atoms.
Where does the name "sinusoidal current" come from? The reason is the production method. Imagine two opposite poles of a magnet, and between them the lines of field strength. Place the frame from the conductor in this field. Its ends are connected to the load, forming a circuit (circuit). Rotate the frame. At the moment when it is parallel to the magnet surfaces, there is no current, since there is no intersection with the tension lines (both sides of the frame are at the same level). Now she turned a little, magnetic field lines cross the conductor, release electrons and a current arises.
At the same time, the other side of the frame also crosses the field, but from the opposite side. The maximum current value is for vertical placement. A sinusoidal current is a graphical representation of this process. Without it, it is difficult to understand the principle of operation of electrical appliances. The graph showing the sinusoidal current is the Cartesian coordinates on the plane. The current is plotted on the vertical axis, and time on the horizontal axis. Since the recorded values periodically repeat when the frame rotates, a sinusoidal current is formed, which changes in direction and magnitude. It is as if the sine wave is strung on the time axis, as part of the waves is located above the axis (positive sign), and part below (negative). The highest wave points correspond to the position of the frame parallel to the field strength lines, and the intersection of the time axis (current is zero) is perpendicular.
The electric circuits of the sinusoidal current are most widely used, since this type of electricity is very easily converted using transformers and other elements of the electric circuit, allowing transmission over long distances, as well as the required modulation. In addition, the principle of generation itself involves the creation of a sinusoidal current.