- 1 What is Electronics?
- 2 Electricity
- 3 Electric Charge
- 4 Electricity and Matter
- 5 Electricity and Conductors
- 6 Black Body Radiation
What is Electronics?
Electronics is the study of flow of electrons in various materials or space subjected to various conditions. In the past, electronics dealt with the study of Vacuum Tubes or Thermionic valves, today it mainly deals with flow of electrons in semiconductors. However, despite these technological differences, the main focus of electronics remains the controlled flow of electrons through a medium. By controlling the flow of electrons, we can make them perform special tasks, such as power an induction motor or heat a resistive coil.
Plumbing Analogy A simple way to understand electrical circuits is to think of them as pipes. Let's say you have a simple circuit with a voltage source and a resistor between the positive and negative terminals on the source. When the circuit is powered, electrons will move from the negative terminal, through the resistor, and into the positive terminal. The resistor is basically a path of conduction that resists the movement of electrons. This circuit could also be represented as a plumbing network. In the plumbing network, the resistor would be equivalent to a section of pipe, where the water is forced to move around several barriers to pass through, effectively slowing its flow. If the pipe is level, no water will flow in an organized fashion, since the pressure is equal throughout the pipe. However, if we tilt the pipe to a vertical position (similar to turning on a voltage source), a pressure difference is created (similar to a voltage difference) and the water begins flowing through the pipe. This flow of water is similar to the flow of electrons in a circuit.
To understand electronics, you need to understand electricity and what it is. Basically, electricity is the flow of electrons due to a difference in electrical charge between two points. This difference in charge is created due to a difference in electron density. If you have a point where the electron density is higher than the electron density at another point, the electrons in the area of higher density will want to balance the charge by migrating towards the area with lower density. This migration is referred to as electrical current. Thus, flow in an electrical circuit is induced by putting more electrons on one side of the circuit than the other, forcing them to move through the circuit to balance the charge density.
In normal conditions all matter has a neutral or has a zero net charge. When an object receives an electron the object becomes negatively charged. When an object gives up an electron the object becomes positively charged. Each charge possesses electric field lines and charge quantities. A positive charge possesses charge quantities of +Q and has electric field lines going outward. A negative charge possesses charge quantities of -Q and has electric field lines going inward. In general, like charges will oppose each other and opposite charges will attract each other. Hence, it is a property of matter.
The force of attraction between two charges can be calculated by Coulomb's Law. Below would be the calculation between a positive and negative charge.
The electric force, F, on a charge, Q, within an electric field, E, are related by Ampere's Law. On an atomic basis, this is the force that gives rise to current.
When a charge in motion passes through a magnetic field. The magnetic field will push a positive charge upward and negative charge downward in the direction perpendicular to the initial direction traveled. The magnetic force on the charge is calculated by Lorennt's Law
The sum of Ampere's Force and Lorentz's Force exert on a charge is called EletroMagnetic Force
Electricity and Matter
All matter interacts with Electricity, and are divided into three categories: Conductors, Semi Conductors, and Non Conductors.
- Matter that conducts Electricity easily. Metals like Zinc (Zn) and Copper (Cu) conduct electricity very easily. Therefore, they are used to make Conductors.
- Matter that does not conduct Electricity at all. Non-Metals like Wood and Rubber do not conduct electricity so easily. Therefore, they are used to make Non-Conductors.
- Matter that conducts electricity in a manner between that of Conductors and Non-Conductors. For example, Silicon (Si) and Germanium (Ge) conduct electricity better than non-conductors but worse than conductors. Therefore, they are used to make Semi Conductors.
Electricity and Conductors
Normally, all conductors have a zero net charge . If there is an electric force that exerts a pressure on the charges in the conductor to force charges to move in a straight line result in a stream of electric charge moving in a straight line
- The pressure the electric force exert on the charges is called voltage denoted as V measured in Volt (V) and defined as the ratio of Work Done on Charge
- The moving of straight lines of electric charges in the conductor is called current denoted as I measured in Ampere (A) and defined as Charge flow through an area in a unit of time
- Conductance is defined as the ratio of current over voltage denoted as Y measured in mho
- Resistance is defined as the ratio of voltage over current denoted as R measured in Ohm
Generally, resistance of any conductor is found to increase with increasing temperature
- R = Ro(1 + nT)
For Semi Conductor
- R = Ro enT
When a conductor conducts electricity, it dissipates heat energy into the surrounding . This results in a loss of electric energy transmitted . If the electric supply energy is PV and the electric loss energy is PR Then the electric energy delivered:
- P = PV - PR
Black Body Radiation
Further experience with conductors that conduct electricity . It is observed that all conductors that conduct electricity exhibit
- Change in Temperature
- Release Radiant Heat Energy into the surrounding
Connect a conductor with an electric source in a closed loop . Plot the value I at different f to have a I - f diagram
- Current increasing with increasing f .
- Radiant heat is a wave travels at velocity v = λf carries energy E = m v2 .
- Current stops increasing .
- Radiant heat is a wave travels at velocity v = c (speed of Light) carries energy E = hfo .
- Current remains at the value of current at fo .
- Radiant heat is a wave travels at velocity v = c (speed of Light) carries energy E = h nfo
- All conductor that conducts Electricity has a threshold frequency fo
- The Radiant Heat Energy is a Light Wave of dual Wave Particle characteristic. Sometimes it behaves like Particle, sometimes it behaves like Wave
- At Frequency f > fo . The energy of the Light is quantized . it can only have the value of multiple integer of fo . E = hf = h nfo