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Study Aid: Capacitance, Resistance and The Chart

This is what I call The Chart. The Chart organizes the basic rules for resistors and capacitors together for reference and reinforcement. I’m usually adjusting it for circumstances, but very little of it really changes. C is capacitance, R is resistance, Q is charge, I is current and V is voltage. Ceq is the variable for the equivalent capacitance of a group of capacitors, Req the equivalent resistance, etc.

The Chart will be your best friend when you study circuits. You will return to it again and again if you stay with electronics.

------------------- Parallel---------------------- Series

Capacitors ------- Ceq = C1 + C2 + ...--------- 1/Ceq = 1/C1 + 1/C2 + ...
------------------- stronger --------------------- weaker
------------------- Qeq = Q1 + Q2 + ... -------- Qeq = Q1 = Q2 = ...

Resistors --------- 1/Req = 1/R1 + 1/R2 + ... --- Req = R1 + R2 + ...
------------------- weaker ---------------------- stronger
------------------- Ieq = I1 + I2 + ... ----------- Ieq = I1 = I2 = ...

Misc ------------- Veq = V1 = V2 = ... -------- Veq = V1 + V2 + ...

The biggest problem people usually have with this is remembering that they have to flip the result of the right side of the “weak” equations. Using and checking units is the main way to fix this. Another way is a shortcut for two capacitors or resistors:

Ceq = (C1 C2)/ (C1 + C2)
You can check this one with units, too: Farads squared on top divided by Farads gives Farads.