Equations - Electricity
I = Current in Amperes (Amps)
V = Voltage (or Potential Difference) in Volts
R = Resistance in Ohms
W = Power in Watts
I = V/R and V = IR and R = V/I
W = I2R and W = V2/R and W = VI
The above hold good for Alternating Current only if the load is purely resistive (rare).
Resistances in Series: R = R1 + R2
Resistances in Parallel: 1/R = 1/R1 + 1/R2
Gain or Loss
Gain or Loss = 10 Log (Output Power/Input Power) = 10Log (P2/P1)
= 20 Log (Output Current/Input Current) = 20 Log (I2/I1)
= 20 Log (Output Voltage/ Input Voltage)
= 20 Log (V2/V1)
e.g. Power Ratios :
2 x = 3 dB approx.
4 x = 6 dB approx.
8 x = 9 dB approx.
10 x = 10 dB
100 x = 20 dB
1,000 x = 30 dB
1,000,000 x = 60 dB