It would seem that revealing the dependence of voltage on frequency is simple. One has only to apply with the appropriate request to the omniscient search engines and … make sure that there is simply no answer to this question. What to do? Let's deal with this difficult issue together.
Voltage or potential difference?
It should be noted that voltage and potential difference are one and the same. In fact, this is the force that is able to make electric charges move in a stream. It doesn't matter where this movement goes.
Potential difference is just another expression for voltage. It is clearer and perhaps more understandable, but it does not change the essence of the matter. Therefore, the main question is where the voltage comes from and what it depends on.
As far as the 220 Volt home network is concerned, the answer is simple. At the hydroelectric power plant, the flow of water rotates the rotor of the generator. The rotational energy is transformed into a voltage force. A nuclear power plant first turns water into steam. He turns the turbine. In a gasoline power plant, the rotor is rotated by the force of burning gasoline. There are alsoother sources, but the essence is always the same: energy turns into voltage.
It's time to ask the question about the dependence of voltage on frequency. But we don't yet know where the frequency comes from.
What is the frequency source
The same generator. The frequency of its rotation turns into the voltage property of the same name. Spin the generator faster - the frequency will be higher. And vice versa.
The tail cannot "wag" the dog. For the same reason, frequency cannot change voltage. Therefore, the expression "voltage versus current frequency" does not make sense?
To find the answer, you need to correctly formulate the question. There is a saying about a fool and 10 pundits. He asked the wrong questions and they couldn't answer.
If you call tension another definition, everything will fall into place. It is used for circuits consisting of many different resistances. "Voltage drop". Both expressions are often considered synonymous, which is almost always wrong. Because the voltage drop can really depend on the frequency.
Why would the voltage drop?
Yes, simply because it cannot help but fall. So. If at one pole of the source the potential is 220 volts, and at the other - zero, then this drop could only occur in the circuit. Ohm's law says that if there is one resistance in the network, then all the voltage on it will drop. If two or more - eachthe drop will be proportional to its value, and their sum is equal to the initial potential difference.
So what? Where is the indication of the dependence of the voltage on the frequency of the current? So far, it all depends on the amount of resistance. Now, if you could find such a resistor that changes its parameters when the frequency changes! Then the voltage drop across it would change automatically.
There are such resistors
They are also called reactive, in contrast to their active counterparts. What do they react to by changing their size? To the frequency! There are 2 kinds of reactances:
- inductive;
- capacitive.
Each view is associated with its own field. Inductive - with magnetic, capacitive - with electric. In practice, they are represented primarily by solenoids.
They are shown in the photo above. And capacitors (below).
They can be considered antipodes, because the reaction to a change in frequency is exactly the opposite. Inductive reactance increases with frequency. Capacitive, on the contrary, falls.
Now, given the features of reactance, in accordance with Ohm's law, it can be argued that the dependence of voltage on the frequency of the alternating current exists. It can be calculated taking into account the values of reactances in the circuit. Just for clarity, we must remember that we are talking about the voltage drop across the circuit element.
And yet it exists
The question mark in the title of the article turned intoexclamatory. Yandex has been rehabilitated. It remains only to give the formulas for the dependence of voltage on frequency for different types of reactances.
Capacitive: XC=1/(w C). Here w is the angular frequency, C is the capacitance of the capacitor.
Inductive: XL=w L, where w is the same as in the previous formula, L is inductance.
As you can see, the frequency affects the value of the resistance, changing it, therefore, changes the voltage drop. If the network has active resistance R, capacitive XC and inductive XL, then the sum of the voltage drops on each element will be equal to the potential difference of the source: U=Ur + Uxc + Uxl.
