Resistors/Capacitors: Parallel vs. Series

[metukah]

I'm trying to think through about what would happen to the total resistance in a circuit in each of the following scenarios, can anyone please help me with the following:

1) 2 resistors in series: what happens to overall resistance if you ADD another resistor in series? (R1 + R2 = Rtotal)
2) 2 resistors in parallel: what happens to overall resistance if you ADD another resistor in parallel? (1/R1 + 1/R2 = Rtotal)

1) 2 capacitors in series: what happens to overall resistance if you ADD another capacitor in series? (1/C1 + 1/C2 = Ctotal)
2) 2 capacitors in parallel: what happens to overall resistance if you ADD another capacitor in parallel? (C1 + C2 = Ctotal)

thanks!

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[PiBond]

I'm trying to think through about what would happen to the total resistance in a circuit in each of the following scenarios, can anyone please help me with the following:

1) 2 resistors in series: what happens to overall resistance if you ADD another resistor in series? (R1 + R2 = Rtotal)
2) 2 resistors in parallel: what happens to overall resistance if you ADD another resistor in parallel? (1/R1 + 1/R2 = Rtotal)

1) 2 capacitors in series: what happens to overall resistance if you ADD another capacitor in series? (1/C1 + 1/C2 = Ctotal)
2) 2 capacitors in parallel: what happens to overall resistance if you ADD another capacitor in parallel? (C1 + C2 = Ctotal)

thanks!

1. increase overall resistance
2. decrease overall resistance

1. decrease overall capacitance
2. increase overall capacitance

as evident, the trend is opposite for capacitors and resistors

 

[metukah]

1. increase overall resistance
2. decrease overall resistance

1. decrease overall capacitance
2. increase overall capacitance

as evident, the trend is opposite for capacitors and resistors

Great! thanks

 

[Silverfalcon]

You shouldn't simply memorize them - it's really important to understand the logic behind them.

A simple way to think about how you would come up with the values. For resistors in series, you would simply add the values to get the overall resistance, right? So, it would increase. But for resistors in parallel, you are now adding the inverses of the values, and then taking the inverse again to remove fraction.

In other words, to get the overall resistance by adding 4 Ohm resistor to a system with 2 Ohm and 3 Ohm in parallel, you are doing (1/2+1/3+1/4)^(-1). Compare this value to (1/2+1/3)^(-1). That's not too easy to do, right?

View it this way. (2+3)^(-1) and (2+3+4)^(-1). The logic remains same because values are positive in both cases. By adding additional number and then taking an inverse, you decrease the overall value. This is why the overall resistances decrease.

 

[fizzgig]

OP note that for caps in series or resistors in parallel

1/R + 1/R = **1/Req**
not
1/R + 1/R = Req

just makin sure...