# Electronics basic formulas

This is just a little collection of formulas and definitions for electronics.

It is not necessary to know a lot of formulas today, since we have so many tools in our PCs and calculators. But sometimes it’s nice to know how things are connected. I use LTSpice a lot, and I do not need to calculate all voltages and currents in a circuit. LTSpice will do that for you. But if you need to cut the voltage of a signal, lower the current or just lower the power, you should absolutely know how the principle of this is to be done.

U = Voltage and is measured in Volt (V) from the German word “Unterschied” (difference) (V or E are often used instead of U. I learned U at school, so I will continue using it)
I = Current and is measured in Ampere (A) from the German word “Intensität” (intensity)
R = Resistance ans is measured in Ohm (Ω)
P = Power and is measured in Watt (W)
C = Capacitance and is measured in Farrad (F)
L = Inductance and is measured in Henry (H) (Why L? Please let me know…)
fc = Cutoff frequency

U = R * I
P = U * I = R * I²
fc = 1/(2*π*R*C)
RMS (Root mean square) of a sinus signal = amplitude / √2

Resistors in series : Rtot = R1 + R2 + R3 + …
Resistors in paralell : Rtot = 1/((1/R1)+(1/R2)+(1/R3)+…)
Capasitors in series : Ctot = 1/((1/C1)+(1/C2)+(1/C3)+…)
Capasitors in paralell : Ctot = C1 + C2 + C3 + …
Inductors in series : Ltot = L1 + L2 + L3 + …
Inductors in paralell : Ltot = 1/((1/L1)+(1/L2)+(1/L3)+…)

yocto(y) = 1E-24 = 0.000000000000000000000001
zepto(z) = 1E-21 = 0.000000000000000000001
atto(a) = 1E-18 = 0.000000000000000001
femto(f) = 1E-15 = 0.000000000000001
pico(p) = 1E-12 = 0.000000000001
nano(n) = 1E-9 = 0.000000001
micro(µ) = 1E-6 = 0.000001
milli(m) = 1E-3 = 0.001
kilo(k) = 1E+3 = 1000
mega(M) = 1E+6 = 1000,000
giga(G) = 1E+9 = 1000000000
tera(T) = 1E+12 = 1000000000000
peta(P) = 1E+15 = 1000000000000000
exa(E) = 1E+18 = 1000000000000000000
zetta(Z) = 1E+21 = 1000000000000000000000
yotta(Y) = 1E+24 = 1000000000000000000000000

In electronics, the range from pico to mega should cover most uses.

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