Direct current is the continuous movement of electrons from the region of negative ( - ) to the region of positive (+) charges through a conductive material, such as a metal wire. Although static discharges are spontaneous movements of charged particles from negative to a positively charged surface, continuous motion of particles through a conductor does not occur.
To create an electron flow, a constant electric current circuit is needed. This is a source of energy (for example, a battery) and a conductor going from the positive pole to the negative. Various electrical devices may be included in the circuit.
Continuous electron motion
Direct current is the continuous movement of electrons through a conductive material, such as a metal wire. Charged particles move toward a positive (+) potential. To create a flow of electricity requires an electric circuit consisting of a DC power source and a wire forming a closed loop. A good example of such a circuit is a flashlight.
Although negatively charged electrons move through the wire to the positive (+) pole of the power source, the current is indicated in the opposite direction. This is the result of an unsuccessful and confusing agreement. Scientists who experimented with currents believed that electricity moves from (+) to ( - ), and this became generally accepted even before the discovery of electrons. In fact, negative charged particles move toward the positive pole, opposite the direction indicated by the direction of current flow. This is confusing, but after the agreement has been adopted, it is already difficult to fix something.
Voltage, current and resistance
Electricity passing through a wire or other conductor is characterized by voltage U, current I, and resistance R. Voltage is potential energy. The current is a stream of electrons in the conductor, and the resistance is the force of its friction.
A good way to imagine a constant electric current is to draw an analogy with the water flowing through a hose. Voltage is the potential that rises at one end of the wire due to an excess of negatively charged electrons. This is similar to the increased pressure of the water in the hose. The potential causes the electrons to move through the wire into the region of the positive charge. This potential energy is called voltage and is measured in volts.
A constant electric current is an electron flux measured in amperes. It is similar to the speed of movement of water through a hose.
Ohm is a unit of measurement of electrical resistance. The atoms of the conductor are arranged so that the electrons pass with little friction. In insulators or poor conductors, atoms show strong resistance or inhibit the movement of charged particles. This is similar to the friction of water in a hose when passing through it.
Thus, voltage is like pressure, flow is like current and hydraulic resistance is like electrical.
DC generation
Although static electricity can be discharged through a metal wire, it is not a direct current source. These are batteries and generators.
In batteries, chemical reactions are used to create direct current electricity. For example, a car battery consists of lead plates placed in a solution of sulfuric acid. When the plates receive a charge from the mains or generator of the car, they change chemically and hold the charge. This direct current source can then be used to power the headlights of a car, etc. The problem is that sulfuric acid is very corrosive and dangerous.
You can make another battery yourself from lemon. It does not require charging, but depends on the acid reaction of different metals. Copper and zinc work best. You can use copper wire or a coin. A galvanized nail can be used as another electrode. Iron will work too, but not so well. It is enough to stick the copper wire and the galvanized nail into a regular lemon and measure the voltage between them with a voltmeter. Some even managed to light a flashlight with this battery.
A reliable source is a generator that is made of wire wound between the north and south poles of a magnet.
Thus, direct current is the continuous movement of electrons from the negative to the positive pole of a conductor, such as a metal wire. For passage of charged particles a chain is needed. In it, the direction of current flow is opposite to the flow of electrons. A circuit is characterized by values such as voltage, current, and resistance. Sources of direct current are batteries and generators.
Electrical circuits
The direct current circuitry consists of a source, to the poles of which are connected conductors connecting the receivers in a closed loop. This is a prerequisite for the passage of current. Chains can be sequential, parallel or combined.
If you take a direct current source, such as a battery, and connect its positive and negative poles with wires to a load , such as a light bulb, an electrical circuit is formed. In other words, electricity flows from one battery contact to another. In series with the lamp, you can install a switch that, if necessary, will regulate the supply of constant electric current.
DC sources
The circuit requires a power source. Typically, a battery or battery is used for this. Another source of energy is a direct current generator. Alternatively, alternating current can be passed through the rectifier. A common adapter used with some portable devices (such as smartphones) converts 220 V AC to 5 V DC.
Conductors
Wires and loads must conduct electricity. Copper or aluminum are good conductors and have low resistance. A tungsten filament in an incandescent lamp conducts current, but has a high resistance, which causes it to heat up and glow.
Serial and parallel connection
In an electrical circuit, several devices, such as light bulbs, can be connected in one line between the positive and negative poles of a battery. Such a connection is called serial. One of the problems with this arrangement is that if one bulb burns out, it acts as a switch and turns off the entire circuit.
The receivers can also be connected in parallel, so that if any lamp goes out, the circuit will not be de-energized. A parallel switching circuit is used not only in Christmas lights - electrical wiring in houses is also carried out in parallel. Therefore, lighting and fixtures can be turned on and off independently of each other.
Ohm's law
The laws of direct electric current include Ohm's law, which is the most fundamental formula for electrical circuits. According to him, the current passing through the conductor is directly proportional to the potential difference on it . The law was first formulated in 1827 by the German physicist Georg Om when he investigated the conductivity of metals. Ohm's law best describes simple DC circuits. Although it is also applicable to alternating current, other possible variables should be considered in this case. The relationship between current, voltage and resistance allows one physical quantity to be calculated if the values of the other two are known.
Ohm's law shows the relationship between voltage, current, and resistance in a simple electrical circuit . In the simplest form, it is written by the equation U = I × R. Here U is the voltage in volts, I is the current in amperes and R is the resistance in ohms. Thus, if I and R are known, U can be calculated. If necessary, the formula can be changed by algebraic methods. For example, if U and R are known and I need to be found, then I should use the equation I = U / R. Or , if U and I are given and R must be calculated, then the expression R = U / I is used.
The importance of Ohm's Law is that if the value of two variables in the equation is known, then a third can be determined. Any of these physical quantities can be measured using a voltmeter. Most voltmeters or multimeters measure U, I, R of direct and alternating electric current.
Calculation of U, I, R
The DC voltage at known current and resistance can be found by the formula U = I × R. For example, if I = 0.2 A and R = 1000 Ohms, then U = 0.2 A * 1000 Ohms = 200 V.
If the voltage and resistance are known, the current can be calculated using the equation I = V / R. For example, if U = 110 V and R = 22000 Ohms, then I = 110 V / 22000 Ohms = 0.005 A.
If voltage and current are known, then R = V / I. If V = 220 V and I = 5 A , then R = 220 V / 5 A = 44 Ohms.
Thus, Ohm's law shows the relationship between voltage, current, and resistance in a simple electrical circuit . It can be applied to both direct and alternating current circuits.
DC power
A charge moving in a circuit (if it is not a superconductor) consumes energy. This may cause the motor to heat up or rotate. Electric power is the speed at which electricity is converted into another form, such as mechanical energy, heat, or light. It is equal to the product of current and voltage: P = U × I. Measured in watts. For example, if U = 220 V and I = 0.5 A , then P = 220 V * 0.5 A = 110 W.