19. Electronics

Electronics

Electronics is the branch of physics and technology concerned with the behaviour and movement of electrons.

Electron Emission: Electron emission is when electrons break free from the surface of a metal. This can happen in a few ways:

1. Thermionic Emission: Heating the metal makes its outer electrons escape.
2. Photoelectric Emission: Shining light on the metal, especially ultraviolet light, causes electrons to break loose.
3. Secondary Emission: When energetic electron beams hit the metal, they knock more electrons loose.
4. Field Emission: Applying a strong electric field to the metal makes electrons pop out.

Diode Valve : A diode valve, invented by J.A. Fleming in 1904, is a device with two parts inside a glass case. One part, called the cathode, gets hot and lets out electrons. These electrons move toward the other part, called the anode, which has a positive charge. This flow of electrons creates an electric current. The cathode emits electrons, which gather around it in a space called a space charge. The diode valve works like a one-way street for electricity, turning alternating current into direct current.

Triode Valve :The triode valve, invented by Lee de Forest in 1907, is a variation of the diode. It has an anode (positive), cathode (negative), and an extra electrode called the control grid. It can do a bunch of jobs like amplifying, generating signals, transmitting, and detecting.

Semi-conductor :Semiconductors are materials that conduct electricity but not as much as conductors like metals, or as little as insulators like rubber. Important ones are germanium and silicon. Inside a semiconductor, some electrons break free from their bonds, leaving behind "holes" which act like positive charges. They're crucial in electronics.

There are two types:

1. Intrinsic Semiconductor: When a semiconductor is super pure, it's called intrinsic.
2. Extrinsic Semiconductor: Adding a tiny bit of impurity to an intrinsic semiconductor boosts its conductivity. These come in two flavors:
• N-type Semiconductor: When the impurity adds extra electrons, making them the majority carriers.
• P-type Semiconductor: When the impurity creates extra holes, making them the majority carriers.

Doping :Doping means adding a bit of impurity to a pure semiconductor. We carefully control the type and amount of impurity.

Donor :Pentavalent impurities are donors.

Acceptor : Trivalent impurities are acceptors.

As the temperature rises, the electrical conductivity of a semiconductor goes up.

Rectifier: A rectifier is a device that changes alternating current (AC) into direct current (DC).

Nanotechnology: Nanotechnology is the study of really tiny stuff.