Electricity plays a huge role in the life of a modern person. However, not everyone understands the principles and value of this phenomenon. The main characteristics of electricity are two dependent quantities: voltage and current. In order to know how they differ from each other, you need to understand their nature. Both that, and another can have both permanent and variable character.
Content
- Physical manifestations
- Analogy with hydraulics
- Relationship of quantities by Ohm's law
- Constant and variable
Physical manifestations
A person can physically feel the manifestations of electricity only indirectly. If you try a battery on your tongue, you can feel a tingling sensation. This is a consequence of the flow of a small current through the body. Sensitive the mucous membrane of the tongue already feels this irritation. Sparks of static electricity can be seen between two charged objects, such as synthetic fabrics, or in a school dynamo experiment. All this is a consequence of the accumulation of charge or potential voltage.
To find out what current strength is, you need to decide on the concept of charge. As you know, all matter in the world consists of atoms. Atoms, in turn, are made up of protons, neutrons, and electrons. Among these particles, only neutrons are neutrally charged. Protons and electrons have potential energy - an electrical charge, which, in particular, keeps atoms in a solid state.
Protons and neutrons are in the nucleus of an atom. Electrons, on the other hand, are located far from the nucleus and move around it in orbits similar to the orbits of the planets of the solar system. The farther the electron is from the nucleus, the less its bond with the center of the atom, and the easier it can be lost. Electrons behave differently in different materials.
In metals, they are weakly bound to the core and freely move within the substance. However, their total number in an object with a neutral charge must always correspond to the number of protons.
If electrons leave the substance due to some action, they carry away the charge with them. Accordingly, the charge remaining in the protons of a substance will be accumulated by this substance. Electrons can carry away a charge in the following cases:
- Friction of two substances against each other.
- Exposure to ultraviolet or radiation.
- Rapid temperature drop.
Thus, a potential difference, or voltage, arises between objects, which can cause a spark. And a spark is already a manifestation of an electric current. Charges of different signs are always attracted to each other. If electrons have passed from one material to another, then one material has accumulated a positive charge, and the other negative.
When they approach, electrons will be attracted to a positively charged body - and a spark will arise. That is, an electric current is the movement of charged cha
Analogy with hydraulics
Word current is derived from the word flow. Accordingly, an analogy can be drawn between the flow of a liquid and an electric current. The flow of liquid is possible from one place to another, only if there is a force that makes it do it. In the simplest case, it is the difference in fluid levels. That is, the potential energy forcing a liquid substance to flow from a higher level to a lower one.
An analogue of the difference in liquid levels is the potential difference or voltage. The analogue of the current will be the pressure of the water flow created by this level difference. Examples of fluid flows:
- Waterfall.
- The flow generated by the water tower.
- Rivers flowing where there is a slope of the territory.
Everywhere, water flows where the level is lower, and the electric current - from higher voltage to lower.
Relationship of quantities by Ohm's law
Electrical values also depend on the material in which it flows. These parameters are determined by the electrical resistance of the substance. Resistance can be both infinitely large for dielectrics, and it can drop to almost zero under superconducting conditions. It depends on the shape of the conductor (its length and cross-section) and the substance from which it is made.
Under normal conditions, resistance is determined by Ohm's law as the ratio of voltage to current in a section of a circuit. That is, the potential difference can be found as the product of current strength and resistance. Knowing how the current strength differs from the voltage is very important for electrical calculations. All the basics of the functioning of electrical circuits are based on this.
Constant and variable
The current and voltage can be either constant or variable. The constancy of the value speaks of its invariability over time. On the contrary, variables change their value periodically over time. If the supply voltage turns out to be variable, then the current strength generated by it will be variable. This means that both of these values will increase and decrease. The waveform can be different:
- Sinusoidal signal (smooth increase - decrease).
- A meander (rectangular, triangular signal) when the value changes sharply.
- A pulsating signal that changes smoothly, then sharply, according to a certain law.
Regardless of whether the current is constant or alternating, its main difference from voltage - the fact that current is the movement of charge carriers, and voltage is the reason for this movement.
