An electrical circuit is a loop which provides a path for electric current (electric charge) to flow. This loop must be closed. In other words, the current must be able to flow from positive to negative terminals otherwise the flow will not take place. The charge is made possible by a source such as a battery which motivates the electrons to move in the conductor. So it is the movement, in other words the flow of these electrons that constitutes the electrical charge. Note that this happens from negative to positive terminal which is the opposite of accepted convention for current direction. In this closed loop we mentioned above, there are components we want, to make our electronic devices possible, such as motors, resistors, inductors capacitors, light bulbs, logic gates and so on.
The loop must be made of conductors. This conductor is most commonly conductive metal wire but other mediums such as conductive polymers or liquids, are also possible. Current can also be carried by electromagnetic induction, which requires no physical medium. Examples include transformers, radio frequency signals.
Conductors are the materials that easily allow flow of electric current upon application of voltage, such as copper.
Conductivity is the measure of how easily current will flow through that material and shown by the symbol σ (sigma). Its unit is Siemens / meter (S/m) but usually milliSiemens / meter is used. It is a characteristic property a material. In other words, it is not affected by the geometry or size of material.
Insulators are the materials that do not allow or very hardly allow the flow of electrical current upon application of voltage. Example: Glass.
Resistivity is the exact opposite of conductivity and shown by the symbol ρ (rho). So if we were to write resistivity in terms of conductivity:
ρ = 1/ σ
And its unit is:
Ohm meter (Ω.m)
Like conductivity, resistivity is also a characteristic property of the material.
Do not confuse resistivity with resistance. Unlike resistivity, resistance is not a characteristic property and depends on geometry of the material. We can find the resistance of a material if we know its resistivity and geometry. So two cables of the same material with different geometries will have different resistance. We calculate resistance from resistivity as below:
R=ρL/A
Here
R: resistance
L: length
A: Area
So this means that as the length of a material increases, the flow of current through it will be more difficult and the resistance will increase. And when its area increases, the resistance will decrease as the current will flow easier.
Semiconductors are the materials that allow flow of current easier than resistors but harder than conductors. Examples: Silicon, Germanium.
In semiconductors, electrons can change their place (thus make current flow possible) only after a certain amount of voltage is applied. By controlling this, we can control when a current will flow or not, depending on our purpose in an electrical circuit. This key principle enables all electrical devices that we use today to function as we want.
Sensors and transducers can sometimes be confused because they both react to some change in their environment but they are not the same thing.
SENSOR
A sensor is a component in an electronic system that can detect (sense) various types of changes in the physical environment and as a result, communicate these to the bigger system it is a part of. In other words they do the same job as what our 5 senses do for us. A sensor can measure how much the change occurs and transmits this information in a convenient format such as electrical signals to the system. The change can be about any physical quality that can be detected and measured, such as light, sound, pressure, acceleration, distance, motion, temperature, humidity and many more.
Most sensors can also be categorized as transducers. So a sensor is a specific type of transducer.
TRANSDUCER
A transducer on the other hand, is a device that converts one form of energy into another. So, while the duty of a sensor is to detect, the duty of a transducer is to transform or convert. Transducers contain sensors. So a transducer is a more general term than a sensor.
Transducers can be separated into two as input and output transducers.
An input transducer takes energy in it and converts it into something such as signals that can be understood.
An output transducer converts signals into energy. For example a motor transforms electrical energy into mechanical energy.
We can look at electronics in two different ways, both of which have different uses, which are analog vs. digital electronics. In short, analog electronics deals with continuous, smoothly varying signals, and digital electronics is about handling discrete signals (which are either on or off or in other words, 1 or 0).
ANALOG ELECTRONİCS
In general sense, analog means something that is comparable to / similar to something else that can continuously vary. This varying thing can be anything such as temperature, pressure, position, voltage…
So in analog electronics, the signals can be represented by varying voltage or current levels proportional to the signal.
The physical quantity is converted to analog signals by a transducer.
Analog electronics has many uses, of which we list only a few below:
It is used for signal amplification, modulation and filtering for purposes such as handling sound and audio communication. Analog systems can be used for radio communication.
Because analog signals are continuous, they can be used to precisely measure and monitor physical quantities by using sensors and transducers.
Voltage regulation and stabilization
Amplifiers, oscillators
ANALOG ADVANTAGES
Because analog signals are continuously, gradually varying, they can represent a lot of different values with high accuracy and resolution, with a very wide range of values.
ANALOG DISADVANTAGES
Much more susceptible to noise and interference than digital systems, which decrease signal quality. Noise susceptibility causes data degradation or even loss, decreases data capacity of analog systems. In long distances this is pronounced even more by introduction of more noise and signals losing energy. Analog filters can be used to reduce noise and signal shaping.
During design it is more difficult to achieve noise reduction and precision.
DIGITAL ELECTRONİCS
Digital electronics deals with digital signals that either take the values on or off. We say digital because the values of on and off are represented by 1 and 0, the digits of binary numbers.
Digital circuits work with logic functions by using AND, OR, NOT logic gates and a few more. From the use of these logic gates, integrated circuits and a whole generation of our electronics devices, anything from digital watches upto supercomputers came into existence.
DIGITAL ADVANTAGES
Digital signals are far more resistant to noise than analog signals because even if there is some noise interference, we can still easily know whether the signal is on or off ( 1 or 0). Distinguishing between different signal levels is easy.
This (1 or 0) is all that matters for us to be able to process that information, unlike analog electronics where the noise can distort the quality of signal which has a wide range of continuously varying values, some of which may be subject to degradation, get lost or change.
Noise resistance, which is the most fundamental advantage of digital electronics and dealing with discrete (1or 0) values have important positive effects:
-Making precise circuits that produce dependable signals and mass producing them is much more easier.
-Dependable, high quality signal transmission over long distances are far more easier. Even in noisy environments, digital signals can be reproduced to its original very easily.
-Data storage is easier.
-Complex operations and a wider range of tasks can more efficiently be handled with digital systems than analog.
DIGITAL DISADVANTAGES
Digital circuits require encoders and decoders, microprocessors, memory components, logic gates, flip flops, intricate coding and algorithms. This can increase costs, complexity and power consumption and make troubleshooting harder.
Digitals signals are not ideal in certain situations where analog signals fit better.
Where high resolution, continuous variations and fine details are needed, analog usually fits better due to its ability to continuously represent values. Analog systems can handle an infinite range of input values. With discrete digital values this is inherently more difficult and some information (quantity and quality) of signal may be lost which can happen during conversion of analog to digital. Some extreme values may not also be represented with digital.
When converting analog to digital signals there can also be delays . Analog systems however do not experience this, as they can represent continuously varying quantities easily. Delay is more pronounced especially during real time applications.
Digital technology progresses at a faster speed therefore obsolescence is more common.
Although the design can be simpler in some situations, making changes to digital design is more difficult. Analog systems are more flexible regarding making changes.