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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%

Example: a component with Yellow, Violet, Orange and Silver bands could be a 47k resistor with 10% tolerance.

Capacitors

A capacitor is a fundamental electronic component that stores electrical energy in an electric field. Think of it like a small, rechargeable battery that can charge and discharge very quickly. At its most basic, a capacitor consists of two conductive plates, typically made of metal, separated by an insulating material called a dielectric. This dielectric can be made of various materials, including ceramic, plastic, or even air. The ability of a capacitor to store charge is known as its capacitance, which is measured in units called Farads (F).

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How Capacitors Work 🔋

Capacitors work by accumulating charge on their conductive plates. When a voltage source, like a battery, is connected across the capacitor, an electric field is created across the dielectric. This causes positive charge to build up on one plate and negative charge to build up on the other. The dielectric prevents the charge from flowing directly between the plates, so the energy remains stored in the electric field. This process is called charging. When the capacitor is connected to a circuit, it releases this stored energy in a rapid burst, a process known as discharging. The amount of charge it can store depends on its capacitance and the voltage applied.

File:Capacitor schematic with details.svg

A basic diagram showing a parallel-plate capacitor connected in a circuit.

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What Capacitors Are Used For 💡

Capacitors are essential in countless electronic devices due to their ability to store and release energy quickly. One of their most common uses is in filtering. In power supplies, they smooth out fluctuations in voltage to provide a steady, clean power source for sensitive electronics. They are also crucial in timing circuits. By controlling how quickly a capacitor charges or discharges, engineers can create precise time delays, which are used in everything from blinking lights to computer clocks.

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Further Applications

Another key application is in signal coupling and decoupling. In audio amplifiers, for instance, they block direct current (DC) while allowing alternating current (AC) signals (like the sound waveform) to pass through, ensuring different stages of the circuit don't interfere with each other's DC voltage levels. In camera flashes, a large capacitor is charged over a few seconds and then rapidly discharged to produce a bright burst of light. From radios and computers to mobile phones and electric vehicles, capacitors are a cornerstone of modern electronics, performing a wide range of critical functions.

Active Components

Microcontrollers

Pages about small computers, programming and process control

Other components

Power

• Batteries

Electrical

Pages pertaining to house and automotive electrical systems