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Electronics

Concepts

• Direct Current (DC) flows in one direction, either steadily or in pulses.
• Alternating Current (AC) flows in alternating directions across a circuit
• Current refers to the quantity of electrons passing a given point.
  • Unit - Amperes
  • Symbol - I
• Voltage - refers to the electrical pressure or force
  • Unit - Volts
  • Symbol - V
• Resistance - refers to a cause of restriction in the flow of a current
  • Unit - Ohms
  • Symbol - R (or Ω)
• Power - refers to the work performed by a current
  • Unit - Watt
  • Symbol - p
• Potential Difference - the difference in voltage between the two ends of a conductor through which a current flows. Also known as voltage drop.

Ohm's Law

a potential difference of 1 volt will force a current of 1 ampere through a resistance of 1 ohm, or: V = I x R or I = V / R or R = V / I

Ohm's law also is used to calculate power where P = I x V (or I^2 x R)

Abbreviations and Units

Metric Prefixes for SI Units

P (PETA_) = x 1,000,000,000,000,000 (or 10^-15)

T (TERA_) = x 1,000,000,000,000 (or 10^-12)

G (GIGA-) = x 1,000,000,000 (or 10^-9)

M (MEG-) = x 1,000,000 (or 10⁶

K (KILO-) = × 1,000 (or 10³

h (HECTO-) = x 100 (or 10²)

d (DECI-) = x 1.0 (or 10^-1)

c (CENTI-) = x 0.01 (or 10^-2)

m (MILLI-) = x 0.001 (or /1000 or 10^-3)

µ (MICRO-) = x 0.000 001 (or /1000000 or 10^-6) (also mc)

n (NANO-) = x 0.000 000 001 (or /1000000000 or 10^-9)

p (PICO-) = x 0.000 000 000 001 (or /10000000000 or 10^-12)

f (FEMTO-) = x 0.000 000 000 000 001 (or /10000000000000 or 10^-15)

Discrete Components

Resistors

R_t = Total Resistance

Resistors in series

• R_t = R1 + R2 + R3 (etc)

Resistors in parallel (2 resistors)

• R_t = (R1xR2) / (R1+R2)

Resistors in parallel (3 or more resistors)

• R_t = 1 / ((1/R1) + (1/R2) + (1/RN))

Resistors used as a voltage divider

• V_out = V_in x (R2/(R1+R2))

Resistor Colour Codes

Colour	Significant Digits (bands 1&2)	Multipliers (band 3)	Tolerence (band 4)
Black	0	1	-
Brown	1	10	±1%
Red	2	100	-
Orange	3	1000 (k)	-
Yellow	4	10000 (x10k)	No
Green	5	100000 (x100k)	colour
Blue	6	1000000 (M)	band
Violet	7	10000000 (x10M)	±20%
Gray	8	100000000 (x100M)	-
White	9	-	-
Gold	-	-	±5%
Silver	-	-	±10%

Active Components

Microcontrollers

Pages about small computers, programming and process control

Other components

Power

• Batteries

Electrical

Pages pertaining to house and automotive electrical systems