Cheat Sheet
Electronics For Dummies Cheat Sheet (UK Edition)
Having basic electronics info with you at your electronics workbench in the UK can be invaluable. Tear out and pin up these calculations, values, symbols, abbreviations, measurements and markings, and you’ll always have the essentials at hand.
Electronics Calculations Using Ohm’s Law and Joule’s Law
These equations, using Ohm’s Law and Joule’s Law, are the most useful you’ll find in electronics. They come in handy all the time for checking what’s going on in your circuits.
Unknown Value  Formula 

Voltage  V = I x R 
Current  I = V/R 
Resistance  R = V/I 
Power  P = V x I or P = V^{2}/R or P = I^{2}R 
where:

V = voltage (in volts)

I = current (in amps)

R = resistance (in ohms)

P = power (in watts)
Resistor and Capacitor Colour Code
Use this table to decipher the colour code on your resistors and capacitors. Distinguishing some colours from others can be tricky, so examine small parts really closely – perhaps with a magnifying glass and always under good light.
Colour  1st Digit  2nd Digit  Multiplier  Tolerance 

Black  0  0  x 1  ± 20% 
Brown  1  1  x 10  ± 1% 
Red  2  2  x 100  ± 2% 
Orange  3  3  x 1,000  ± 3% 
Yellow  4  4  x 10,000  ± 4% 
Green  5  5  x 100,000  – 
Blue  6  6  x 1,000,000  – 
Violet  7  7  x 10,000,000  – 
Grey  8  8  x 100,000,000  – 
White  9  9  –  – 
Gold  –  –  x 0.1  ± 5% 
Silver  –  –  x 0.01  ± 10% 
Capacitor Tolerance Code
Capacitor ratings aren’t all that precise, but you can at least work out how imprecise the ratings are by deciphering the following letter tolerance codes.
Code  Tolerance 

B  ± 0.1 pF 
C  ± 0.25 pF 
D  ± 0.5 pF 
F  ± 1% 
G  ± 2% 
J  ± 5% 
K  ± 10% 
M  ± 20% 
Z  +80%, –20% 
Capacitor Value Reference
The first two digits of a capacitor value reference give you a number that you then divide or multiply by factors of ten according to the value of the third digit.
Marking  Value (in microfarads – µF – unless otherwise stated) 

Nn  Picofarads (nn is a number from 01 to 99) 
101  100 pF 
102  0.001 
103  0.01 
104  0.1 
221  220 pF 
222  0.0022 
223  0.022 
224  0.22 
331  330 pF 
332  0.0033 
333  0.033 
334  0.33 
471  470 pF 
472  0.0047 
473  0.047 
474  0.47 
Common Electronic Component Symbols in the UK
This table shows you the electrical and electronic component symbols used in the UK. The US and other countries use their own symbols for some components, such as resistors and capacitors.
Electronic Component Abbreviations
This table lists the abbreviations for some standard international units named after famous scientists and engineers. The symbol for the ohm is the upper case omega, which is the last letter of the Greek alphabet.
Units of Measure for Electronics and More
These units of measure are used in many different areas, not just electronics. Note that in science and engineering, though, an upper case ‘M’ represents a million and a lower case ‘m’ represents a millionth.
Number  Name  Scientific Notation  Prefix  Abbreviation 

1,000,000,000  1 billion  10^{9}  giga  G 
1,000,000  1 million  10^{6}  mega  M 
1,000  1 thousand  10^{3}  kilo  k 
100  1 hundred  10^{2}  –  – 
10  ten  10^{1}  –  – 
1  1  10^{0}  –  – 
0.1  tenth  10^{–1}  –  – 
0.01  hundredth  10^{–2}  –  – 
0.001  thousandth  10^{–3}  milli  m 
0.000001  millionth  10^{–6}  micro  µ 
0.000000001  billionth  10^{–9}  nano  n 
0.000000000001  trillionth  10^{–12}  pico  p 