Basics of Electronics

The field of electronics is a branch of physics and electrical engineering that deals with the emission, behavior, and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification and rectification, which distinguishes it from classical electrical engineering, which only uses passive effects such as resistance, capacitance, and inductance to control electric current flow.

History of Electronics

Electronics have hugely influenced the development of modern society. The identification of the electron in 1897, along with the subsequent invention of the vacuum tube which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age.[1] Practical applications started with the invention of the diode by Ambrose Fleming and the triode by Lee De Forest in the early 1900s, which made the detection of small electrical voltages such as radio signals from a radio antenna possible with a non-mechanical device.

Bassic terms in Electronics

Current

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits, the charge carriers are often electrons moving through a wire. In semiconductors, they can be electrons or holes. In an electrolyte, the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.

The SI unit of electric current is the ampere, or amp, which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit. Electric current is measured using a device called an ammeter.

Voltage

Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage is named volt.

The voltage between points can be caused by the build-up of electric charge (e.g., a capacitor), and from an electromotive force (e.g., electromagnetic induction in generators, inductors, and transformers. On a macroscopic scale, a potential difference can be caused by electrochemical processes, the pressure-induced piezoelectric effect, and the thermoelectric effect.

A voltmeter can be used to measure the voltage between two points in a system. Often a common reference potential such as the ground of the system is used as one of the points. A voltage can represent either a source of energy or the loss, dissipation, or storage of energy.

Resistance

Resistance to electricity–that is, electrical resistance–is a force that counteracts the flow of current. In this way, it serves as an indicator of how difficult it is for current to flow. Resistance values are expressed in ohms (Ω).

Electricity will flow from high to low when an electron differential exists between two terminals. Resistance counteracts that flow. The greater the resistance, the lower the current. Conversely, the lower the resistance, the greater the current.

What are resistors?

Resistors are electronic components that resist the flow of electricity in a circuit. Resistors are used in electric circuits to adjust current and voltage, much like faucets are used to adjust the tap water flow. They can be used not only to control the flow of current but also to distribute voltage in a circuit.

Electronic circuits need resistors in order to operate under appropriate conditions. Resistors are made of materials that resist the flow of electricity as it passes through them. In this way, they can control the flow of current throughout a circuit. When the current is reduced by a resistor, the surplus electrical energy is converted into heat.

DC series and Parallel circuits

Circuits consisting of just one battery and one load resistance are very simple to analyze, but they are not often found in practical applications. Usually, we find circuits where more than two components are connected together. There are two basic ways in which to connect more than two circuit components: series and parallel.

Series

Here, we have three resistors (labeled R1, R2, and R3), connected in a long chain from one terminal of the battery to the other. (It should be noted that the subscript labeling -- those little numbers to the lower-right of the letter "R" -- are unrelated to the resistor values in ohms. They serve only to identify one resistor from another.) The defining characteristic of a series circuit is that there is only one path for electrons to flow. In this circuit, the electrons flow in a counter-clockwise direction, from point 4 to point 3 to point 2 to point 1 and back around to 4.

Parallel

Again, we have three resistors, but this time they form more than one continuous path for electrons to flow. There's one path from 8 to 7 to 2 to 1 and back to 8 again. There's another from 8 to 7 to 6 to 3 to 2 to 1 and back to 8 again. And then there's a third path from 8 to 7 to 6 to 5 to 4 to 3 to 2 to 1 and back to 8 again. Each individual path (through R1, R2, and R3) is called a branch.

The defining characteristic of a parallel circuit is that all components are connected between the same set of electrically common points. Looking at the schematic diagram, we see those points 1, 2, 3, and 4 are all electrically common. So are points 8, 7, 6, and 5. Note that all resistors as well as the battery are connected between these two sets of points.

Kirchhoffs Current Law

This law also called Kirchhoff's first law, or Kirchhoff's junction rule, states that, for any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node; or equivalently

The algebraic sum of currents in a network of conductors meeting at a point is zero.

kirchhoff's law of voltage

According to Kirchhoff's Voltage Law, The voltage around a loop equals the sum of every voltage drop in the same loop for any closed network and equals zero. Put differently, the algebraic sum of every voltage in the loop has to be equal to zero and this property of Kirchhoff's law is called conservation of energy.