๐ 21 Calculators
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๐ง Resistor Color Code
8.2 kโฆ
๐ SI Prefixes
| Prefix | Symbol | Multiplier |
|---|---|---|
| Tera | T | 1012 |
| Giga | G | 109 |
| Mega | M | 106 |
| Kilo | k | 103 |
| Milli | m | 10-3 |
| Micro | ยต | 10-6 |
| Nano | n | 10-9 |
| Pico | p | 10-12 |
△ Ohm’s Law Triangle
Cover V to find V = I × R
Cover I to find I = V / R
Cover R to find R = V / I
๐ AWG Wire Table
| AWG | Diameter | โฆ/1000ft | Max Amps |
|---|---|---|---|
| 10 | 2.588 mm | 0.999 | 30 A |
| 12 | 2.053 mm | 1.588 | 20 A |
| 14 | 1.628 mm | 2.525 | 15 A |
| 16 | 1.291 mm | 4.016 | 10 A |
| 18 | 1.024 mm | 6.385 | 5 A |
| 20 | 0.812 mm | 10.15 | 3.5 A |
⚖ Copper & Aluminum Resistivity
| Material | Resistivity (ฮฉ·m) | Temp. Coeff. |
|---|---|---|
| Copper | 1.68 × 10-8 | 0.00393 /°C |
| Aluminum | 2.65 × 10-8 | 0.00403 /°C |
| Silver | 1.59 × 10-8 | 0.00380 /°C |
| Gold | 2.44 × 10-8 | 0.00340 /°C |
๐ Standard Voltages & Fuse Ratings
| Standard Voltages | Common Fuse Ratings |
|---|---|
| 3.3V, 5V, 9V, 12V | 0.5A, 1A, 2A |
| 24V, 48V (Industrial) | 3A, 5A, 10A |
| 110V / 120V (AC) | 13A, 15A, 20A |
| 220V / 230V / 240V (AC) | 30A, 32A, 40A |
๐ก Electronics Symbols
Battery
Resistor
Capacitor
Inductor
Diode/LED
AC Source
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Learn the Fundamentals
Core electrical engineering concepts explained simply
Ohm’s Law
Ohm’s Law states that the voltage across a conductor is directly proportional to the current through it, given constant resistance: V = I × R. It is the foundation of nearly every calculation in this suite.
AC vs DC
Direct current (DC) flows in one constant direction, as from a battery. Alternating current (AC) periodically reverses direction, as from a wall outlet, and is described by frequency, amplitude and phase.
Kirchhoff’s Laws
Kirchhoff’s Current Law states that current entering a node equals current leaving it. Kirchhoff’s Voltage Law states that the sum of voltages around any closed loop equals zero.
Power Formula
Electrical power is the rate of energy transfer, calculated as P = V × I. Combined with Ohm’s Law it can also be written as P = I²R or P = V²/R.
Voltage Divider
A voltage divider uses two series resistors to produce an output voltage that is a fraction of the input voltage: Vout = Vin × R2 / (R1 + R2).
Capacitors
A capacitor stores electrical energy in an electric field between two plates. Its charge is Q = CV and stored energy is E = ½CV².
Inductors
An inductor stores energy in a magnetic field and opposes changes in current. Its behavior in a circuit is described by the RL time constant, ฯ = L/R.
Transformers
A transformer transfers energy between two coils through electromagnetic induction. The voltage ratio equals the turns ratio: Vs/Vp = Ns/Np.
Reactance
Reactance is the opposition to AC current from capacitors and inductors. Inductive reactance XL = 2ฯfL increases with frequency, while capacitive reactance XC = 1/(2ฯfC) decreases with frequency.
Impedance
Impedance combines resistance and reactance into a single value describing total opposition to AC current: Z = √(R² + (XL − XC)²).
Power Factor
Power factor is the ratio of real power to apparent power in an AC circuit, describing how effectively current is converted into useful work. A power factor of 1 means voltage and current are perfectly in phase.
Electrical Safety
Always de-energize circuits before working on them, use properly rated fuses and breakers, never exceed a wire’s rated ampacity, and treat every circuit as live until verified otherwise with a meter.