Electronics and electricity is a bit difficult to learn, and this can be solved by making an analogy between hydraulic circuits and electrical circuits . In this way, everything is understood in a more intuitive way. Whether you are an amateur or a student, surely this tutorial will help you a lot…
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Analogies between magnitudes
Hydraulic systems, through which a liquid circulates, such as water, and electrical circuits, through which electrons circulate, have similarities. That is why we are going to make this analogy between the main magnitudes of both cases:
- Volume in liters (l) = Electric charge in coulombs (C)
- Flow in liters per second (l/s) = Current intensity in Coulombs per second or Amperes (C/s or A)
- Pressure in pascals (Pa) = Voltage in volts (V)
- Hydraulic energy (Pa liter –> Joules) = Electrical energy (V C = Joules)
- Power is pressure Flow = Watts (W) = Power is Voltage Current = Watts (W)
1 J/s = W
As you can understand, the hydraulic and electrical analogy is useful to better visualize or understand what happens in the electrical circuit. You only have to think about what would happen in a water circuit, for example, and you can also begin to understand what happens in an electrical circuit. The difference is that instead of H20 (water) molecules, electrons circulate …
For example:
- Hydraulic circuit : imagine that you have a glass of water, and you insert a tube into it that goes to a small hydraulic pump to extract water, and this is led through a tube until it falls back into the glass again. During the route there is a small narrowing in the pipe before the end of the tube that returns to the pool. In this case, the pump raises the water in the vessel at 0 pressure and pressurizes it, for which it requires energy. This is how water flows under pressure. And when the water is released under pressure, the pressure returns to 0 and stored energy is released.
- Electrical circuit : a battery brings charge from ground to 0v (negative terminal), from the positive terminal it raises the charge to a higher voltage, which requires power. The charge flows under the increased voltage and passes through a resistor before returning to ground. And when the charge is released, the voltage drops back to zero and the stored energy is released.
conductor vs insulator
As you well know, in hydraulic circuits you have tubes through which the fluid circulates, and you may also have obstacles that prevent the flow from being interrupted. In the same way, in electrical circuits there are also similar elements.
On the one hand we have the conductors , which can be considered as the tubes through which the electrons of the current that flows through them travel. While, on the other hand, we have insulators , which are materials that prevent this flow of electrons from occurring.
- Conductor : is a material that offers little resistance to the movement of electric charge. Its atoms are characterized by having few electrons in their valence shell, so it does not take much energy for them to jump from one atom to another.
- Insulator or dielectric : it is a material whose internal electrical charges cannot move causing a small magnitude of current under the influence of an electric field, unlike conductive and semiconductor materials, which easily conduct an electric current
On the other hand, on the electricity side we also have what are known as semiconductors , which we will talk about later in the section on transistors and diodes. But basically, you have to understand that a semiconductor is an element that behaves either as a conductor or as an insulator depending on various factors, for example: the electric or magnetic field, the pressure, the radiation that hits it, or the temperature of the environment in which it is located, etc.
energy and power
In a hydraulic circuit where water flows under pressure, we have to:
- Energy = Pressure Volume
- Power = Pressure Flow
While in an electrical circuit , where a charge circulates through a conductor, we have to:
- Energy = Voltage · Charge –> E = V · C
- Power = Voltage Current –> P = V I
According to Ohm’s Law , which says:
Therefore, the power could also be calculated :
Endurance
A hydraulic resistance is a narrower section of a pipe. This causes the pressure to drop, similar to an electronic resistor which is a poorer conducting material causing a voltage drop in the direction of flow. In a hydraulic circuit the pressure drop (voltage) across the resistor is proportional to the flow rate (current) through the resistor.
In electrical circuit, resistance is measured in ohms (Ω) . And, based on Ohm’s Law seen above, you should already know how to calculate it. The higher the number of ohms in a resistor, the more resistance it offers to advancement, that is, as if the taper were greater in the pipe.
Similar to the hydraulic circuit, the more water pushed through the constriction in the pipe, the greater the pressure drop at that point. In an electrical circuit, potential energy is transformed into heat as it passes through resistance.
Condenser
Here I compare the behavior of condensers and that of a water tank . As you know, the volume of stored water is equal to the product of the capacitance times the pressure:
Flow = Capacitance x change in pressure with time
Something similar happens in an electrical capacitor. We have a set of two parallel metal plates separated by an insulator or dielectric. When we apply a voltage across the capacitor, the charge is stored in this capacitor, as if it were a reservoir of electrons. And in this case it would be:
Charge = Capacitance Voltage
For example, if we have a 0.01 Farad capacitor and a 12 Volt circuit, then the charge in this case would be 0.12 Coulombs. As you should know, the capacitance or capacity of the capacitor is measured in coulombs per volt, which is the equivalent of farads.
We can also say that:
Current = Capacitance Voltage change per unit of time.
For example, if we have that same capacitor of 0.01 F and a variation of 10v/s, then it would give us 0.1 A of current.
On the other hand, we have that the energy storage would be:
- Hydraulic energy = 1/2 Pressure Volume
- Electrical energy = 1/2 Voltage Charge
While for the hydraulic circuit the energy stored comes from the pump that pushes the water towards the tank, in the electrical circuit the energy stored in the condenser comes from the power supply or battery.
If you connect a resistor across the two terminals of the capacitor, energy can be extracted, causing a current to flow through the resistor. In this case, both the current and the voltage drop exponentially until the voltage reaches 0 and all the energy has been dissipated as heat in the resistor.
It should also be noted that charge is conserved even as a capacitor charges and discharges. When you connect a battery to a capacitor, the battery draws positive charge from one side of the capacitor, leaving a deficit, or negative charge, on that side, and sends positive charge on the other side.
For example , imagine you connect a 100v battery to a 1F capacitor, which will cause it to draw 40C of charge on the positive side of the capacitor and leave -50C on the negative side. That is, the net charge on the capacitor at that time would be 0 (50 – 50), but a difference of 100 C on the two sides. When the battery is disconnected, the potential difference or voltage remains because the charge is trapped in the capacitor.
The physical attraction of the opposite charges holds the positive and negative charge in place. That is why the metal plates of the capacitor are very close together, so that this phenomenon of attraction occurs. An electric field exists in the space between the two plates, causing any charged object in that space to feel a force. For example, a free electron is attracted to the positively charged plate and repelled by the negatively charged plate.
If you short the two terminals of the capacitor, the positive charge will go to the negatively charged side, bringing the charge back to zero on both sides.
Transistor
The transistor is a semiconductor device very present in today’s electrical and electronic circuits. However, it is a great unknown to many. For this reason, I am going to make an analogy with water as I have done previously with the rest of the components, and you will see how you understand it much better.
The analogy can be made between a transistor and a faucet . Similar to a transistor, in a faucet that is connected to a water source, the faucet allows the flow of water to drain through it to a sink. The knob or handle that activates the faucet can be understood as a door. That is to say:
- Source : it is as a source (source) or emitter of the transistor, which can pass the current coming from the power source to the sink.
- Stopcock or knob : it is like the gate (gate) or base of the transistor, which allows to activate or deactivate, that is, to let flow pass or not. Like some kind of electrically controlled switch.
- Sump : it is like the drain or collector of the transistor, where the water comes out, in this case the current. But only when the door allows it.
Thus, by driving the gate, it can be made to flow (1 or on) or not flow (0 or off), and this is how transistors work. That is to say:
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When the gate of a transistor is open , then electricity flows from the source to the sink and the transistor is said to be on.
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Otherwise, when a transistor’s gate is closed , electricity does not flow from source to sink, and the transistor is said to be off.
Diode
The diode is also another semiconductor device like the transistor but with differences. In this case, it can be likened to a one-way valve, allowing water to only flow in one direction and not the other through a tube.
Something similar happens in a diode, and that is that the flow of electrons or current can only travel in one direction , while it is throttled in the other.
As you know, there are several types of diodes. For example, in an LED we have something similar to the above, it will also allow current to pass in only one direction, but imagine that the tube through which it travels has a perforation, and it allows a certain amount of water to pass to the outside. In the case of the LED diode, this leaked energy will be transformed into light.
More information in our tutorial on basic electronic devices .
Inductor
In the case of the inductor , we could also make a similarity. For example, imagine a paddle wheel (ferris wheel) with a rigid axis attached to a flywheel, and through which a stream of water passes to move it.
In this way, when pressure is applied to the blades of the wheel, the wheel is rotated, also turning the flywheel to which it is connected. As pressure is applied over time, the stone will spin faster and faster. Once spinning, by inertia, the stone will continue to rotate even when the pressure has been removed, keeping the flow of water at a constant speed even without external forces, until a negative pressure is applied…
In this case we have to:
Moment or torque = Inductance Flow
This is much like when people go through a revolving door. If people are in a hurry, they push the revolving door by applying positive pressure, which causes the door to accelerate and gain momentum. If people are more relaxed, they will walk at the rate at which the door rotates automatically, since it maintains a constant speed or momentum. And if some very slow people pass by, the door catches up with them and pushes them (negative pressure), which will slow down the door.
In the case of an electrical inductor , it is a coil of conducting wire wrapped around a cylindrical core. When a voltage is applied to the inductor, magnetic flux builds up in the coil. The magnetic flux is like the impulse of the flywheel, so current will continue to flow even when the voltage source has been removed:
Current flow = Inductance Current
Flux can be measured in Webers, while inductance is in Henries and current in Amps, as you should know if you know Maxwell’s equations.
For example , if 20v is applied to an inductor, and the inductance is taken to be 20 henries, then we have:
20 volts = 20 Henrys Coulombs
If we clear the coulombs or amperes/second, we have that in this case the flow rate would increase by 1 A/s or 1 C. If this is the case, when 0v is applied, the constant current flow will continue, and if -20v is applied, causes the current to drop 1A every second…
On the other hand, just as it can be done with the kinetic energy of a hydraulic circuit, the energy of a circuit with an inductor can also be calculated:
Hydraulic power = 1/2 Inductance Flow 2
Electrical energy = 1/2 Inductance Current 2
In the case of the hydraulic, the stored energy comes from the pump that pushed the water through the inducer or the current of the river. In the case of electronics, the stored energy comes from the battery that pushed the charge through the inductor and built up magnetic flux through the coil.
Oscillator (LC)
If a capacitor is connected to the ends of an inductor then an oscillator is created . This oscillator, once started, causes charge to flow back and forth between the two terminals at a fixed frequency, even after the maximum charge, voltage, and current decrease.
In the case of the hydraulic oscillator , as we have said before, it would be like connecting a tank with a flexible membrane that separates the two sides of the tank, to a waterwheel. Since the membrane will oscillate to one side and the other, that will generate the oscillation. However, when the sheet or membrane reaches a neutral position, the pressure is at zero, but the moment or couple of the wheel of the wheel and the water current are at their maximum.
In the case of the electronic oscillator , we have a circuit made up of an inductor and a capacitor (LC):
- You begin by charging the capacitor from a battery or power source.
- The potential energy stored in the electric field maintains the charge on both sides of the capacitor.
- By disconnecting the battery or source, the inductor and capacitor connect, allowing the circuit to run freely.
- The voltage from the capacitor forces the accumulated charge through the inductor, which causes magnetic flux to build up in the inductor.
- The magnetic flux is like the impulse, when the capacitor runs out of charge, the voltage is 0, but the current flow is at its maximum.
- The magnetic flux then forces the current to continue flowing to the opposite side of the capacitor, raising the voltage and accumulating charge in the opposite direction.
- When the magnetic flux runs out of power and current stops flowing, the capacitor is fully charged in the opposite direction, beginning a cycle again.
- Now everything runs in reverse…
In this case, we have to:
Period = 2 π √ (Inductance · Capacitance)
Frequency = 1/Period
As you can see, the frequency of the oscillator does not depend on the amount of load. Charging the capacitor further increases the amplitude of the voltage and current, but will not change the frequency. Like a guitar string, it vibrates at the same frequency whether it is finger-bridged softly or hard, producing the same note in either case. Only the volume is affected…
Conclusion about electronics and electricity
As you can see, electricity and electronics are not that complex if you compare them to a hydraulic circuit, which is somewhat more intuitive, since you can imagine the flow of water that passes through it and what happens. On the other hand, in the case of electric current, since electrons are invisible to the eye and that circulate inside the materials, it is not understood in such a graphic way.