Monday, November 23, 2015

Getting Started in Electronics by Forrest Mims Notes

Getting Started in Electronics by Forrest Mims


Chapter 1 - Electricity

Ions - Atoms are normally balanced, but when an electron is removed from a balanced atom it becomes a positive ion, and conversely when a stray electron attaches to a balanced atom it will become negatively charged as a negative ion.

Electrons - Electrons can rest on a surface or travel nearly the speed of light. (186,000 mps). When electrons rest on a surface this surface an be said to have a negative static electrical charge. Electrical current is what we call electrons in motion. Resting electrons can be put into motion by positive ions as they attract the free electrons to balance the atom by filling the electron gaps.

Electrons are removed through friction, heat, light, and chemicals to create positive ions and a surface with resting positive ions has a positive static electrical charge.

"Electron" is named after the Greek word for "amber". Amber is easily electrified by friction.

Electrons can travel through moist air and leak away on a humid day.

Like charges repel, unlike charges attract. 

Conductors - Materials through which electrons travel: silver, gold, iron, copper, etc.
Insulators - Materials through which electrons travel poorly or not at all: glass, plastic, rubber, wood

Direct Currents (DC) - current through a conductor that can only flow in one direction.

  • Current(I)- quantity of electrons passing a given point in units of amperes. One ampere = 6,280,000,000,000,000,000 (6.28 x 10 (to the 18th power))
  • Voltage (V or E)- Electrical pressure or force. Sometimes referred to as potential. Voltage Drop is the difference between voltages at two ends of a conductor.
  • Power or Watt (P) - Work performed by an electrical current. Power of DC = voltage x amps.
  • Resistance (R) - Resist current in Ohms. Resistence of a conductor is its VD / I.
Ohm's Law
V= I x R
I = V / R
R = V / I
P = V x I (or) I(squared) x R

Page 15: Explain in 25 words how the straw/nail motor works:

The nail inside the straw is magnetized by the coil of wire connected to the battery. As the current flows it is "tugged" either way by the positive charge in its center. 

Making DC Electricity:
  • electrolytes - chemical DC generators. A solution that contains many ions may be broken down and conductors can utilize the positive ions and negative ions to create a current in a "wet cell". "Dry cells" would be that where an electrolyte is absorbed by paper or formed into a paste. The lemon battery.
  • electromagnets - A moving magnet can generate a field of DC in the direction the magnet is pushing.
  •  thermoelectric generators - heating two dissimilar metals will create a difference in voltage between the two materials in what is called a seeback effect.
Alternative Currents (AC)
The direction or polarity of a current can be altered or reversed resulting in an alternating current.

transformer: A wire carrying AC will induce a current in a nearby wire. (used for long distance powerlines)

electrical circuit - allows current to flow.

  • A basic circuit has a power source and a load. A load can be a lamp, motor, etc.
  • A series circuit may include more than one load and the current flows directly through one component to another.
  • A parallel circuit is when multiple components are connected to a power source but do not have to flow from one component to another. 
  • A series parallel circuit includes both components wired in a series and in a parallel.
electrical short circuit: when a conductor allows electricity to take a shortcut around a circle it can "short circuit" damage the components or even causing harm to you.
electrical ground: protects from shock hazard by reducing voltage to 0.

Pulse - sudden, brief increase or decrease in a current flow.
Wave- A periodic fluctuation in a current or voltage.
Signal - Periodic waveform that conveys information. The process that generates the waveform is called modulation.
Noise - Small, random unwanted electrical currents in all electrical devices and circuits.

Chapter 2 - Electronic Components

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