Electronic Formula Notation Calculations
| C E e G I i k L M N P |
capacitance voltage source instantaneous E conductance current instantaneous I coefficient inductance mutual inductance number of turns power |
[farads, F] [volts, V] [volts, V] [siemens, S] [amps, A] [amps, A] [number] [henrys, H] [henrys, H] [number] [watts, W] |
Q q R T t V v W F Y y |
charge instantaneous Q resistance time constant instantaneous time voltage drop instantaneous V energy magnetic flux magnetic linkage instantaneous Y |
[coulombs, C] [coulombs, C] [ohms, W] [seconds, s] [seconds, s] [volts, V] [volts, V] [joules, J] [webers, Wb] [webers, Wb] [webers, Wb] |
Resistances
The resistance R of a circuit is equal to the applied direct voltage E divided by the resulting steady current I:
R = E / I
Resistances In Series Calculation
When resistances R1, R2, R3, … are connected in series, the total resistance RS is:
RS = R1 + R2 + R3 + …
Resistances in Parallel
When resistances R1, R2, R3, … are connected in parallel, the total resistance RP is:
1 / RP = 1 / R1 + 1 / R2 + 1 / R3 + … Alternatively, when conductances G1, G2, G3, … are connected in parallel, the total conductance GP is:
GP = G1 + G2 + G3 + …
where Gn = 1 / Rn
For two resistances R1 and R2 connected in parallel, the total resistance RP is:
RP = R1R2 / (R1 + R2)
RP = product / sum
The resistance R2 to be connected in parallel with resistance R1 to give a total resistance RP is:
R2 = R1RP / (R1 – RP)
R2 = product / difference
Capacitances
When a voltage is applied to a circuit containing capacitance, current flows to accumulate charge in the capacitance:
Q = òidt = CV
Alternatively, by differentiation with respect to time:
dq/dt = i = C dv/dt
Note that the rate of change of voltage has a polarity which opposes the flow of current.
The capacitance C of a circuit is equal to the charge divided by the voltage:
C = Q / V = òidt / V
Alternatively, the capacitance C of a circuit is equal to the charging current divided by the rate of change of voltage:
C = i / dv/dt = dq/dt / dv/dt = dq/dv
