There are two kinds of currents in electricity - direct and alternating. Devices also require one or the other type of current to supply power. The possibility of their work depends on this, and sometimes their integrity after being connected to the wrong power supply. We will describe the difference between alternating current and direct current in this article, giving a short answer in the most simple words.
Content:
- Definition
- Origin
- DC Formulas
- AC formulas
Definition
Electric current is the directional movement of charged particles. This is the definition from a physics textbook. In simple words, it can be translated so that its components always have some direction. Actually, this direction is the defining one in today's conversation.
Alternating current (AC) differs from direct current (DC) in that the latter has electrons (charge carriers) always moving in the same direction. Accordingly, the difference between alternating current is that the direction of movement and its strength depend on time. For example, in an outlet, the direction and magnitude of the voltage, respectively, and the current strength, change according to a sinusoidal law with a frequency of 50 Hz (the polarity between the wires changes 50 times per second).
For dummies in electrics, so to speak, we will depict this on a graph, where polarity and voltage are shown along the vertical axis, and time along the horizontal:
The red line shows a constant voltage, it remains unchanged over time, except that it changes when switching a powerful load or short circuit. Green waves show sinusoidal current. You can see that it flows in one direction or the other, in contrast to direct current, where electrons always flow from minus to plus, and the direction of movement of the electric current is chosen from the plus to the minus.
Simply put, the difference in these two examples is that the constant always has plus and minus on the same wires. If we talk about a variable, then the concepts of phase and zero are used in power supply. If viewed by analogy with a constant, then the phase and zero are plus and minus, only polarity changes 50 times per second (in the USA and a number of other countries 60 times per second, and in airplanes more than 400 times).
Origin
The difference between AC and DC lies in their origin. Direct current can be obtained from galvanic cells such as batteries and accumulators.
It can also be obtained using a dynamo - this is an outdated name for a DC generator. By the way, with their help, energy was generated for the first power grids. We talked about this in the article about Nikola Tesla's discoveries, in notes on the war of ideas between Tesla and Edison. Later, this was the name of small generators for powering bicycle headlights.
Alternating current is also produced with the help of generators, nowadays mainly three-phase.
Also, both voltages can be obtained using semiconductor converters and rectifiers. So you can rectify alternating current or get it by converting direct current.
DC Formulas
The difference between change and constant are also formulas for calculating the processes occurring in the chain. So the resistance is calculated by Ohm's Law for a section of a chain or for a complete chain:
E = I / R
E = I / (R + r)
Power is also easy to calculate:
P = UI
AC formulas
In the calculations of alternating current circuits, the difference in the formulas is due to the difference in the processes occurring in the capacitors and inductors. Then the Ohm's law formula will be for active resistance:
For capacity:
For inductance:
Here 1 / wC and wL are capacitive and inductive reactances, and w is the angular frequency, it is equal to 2piF.
For a circuit with capacitance and inductance:
wL-1 / wC is reactance, it is denoted as Z.
The video below explains in more detail what is the difference between alternating current and direct current:
Related materials:
- How to increase DC and AC voltage
- What is active, reactive and apparent power
- What is line and phase voltage
