capacitors

[NWDS]

can you work this one out pls,

2 capacitors, 1@ 10uf and the 2nd @ 20uf in series, when they are connected in series there combined effect would be the equivalent to a capacitor of 6.66

I have worked this out but the figures in the book are different, would one of you kind gents/ladies pls work it out and post your answer ???

regards NWDs

 

[springcrocus]

Capacitors work the opposite way to resistors. Capacitors in parallel add together, capacitors in series use 1/C1 + 1/C2 or C1 x C2 / C1 + C2

10 x 20 / 10 + 20 = 6.66

Your answer of 6.66uF is correct.

 

[NWDS]

Thanks SC, I have worked it out as below

1/10= 0.1, 1/20=0.05, add 0.1+0.05= 0.15, 1/0.15= 6.66

Regards NWDS

 

[seajayess]

What are they asking for total capacitance or capacitance reactance you are correct that capacitors in series you just cant add them together and you both get the same answer but if you require capacitance reactance you need to divide 10 and 20 by 1000000 to bring it down to Farads then take your answer and work out total capacitance reactance to get resistance ohms take it it is 50 hertz supply and 3.1415 = pie

1

2 X 3.1415 X 50 X 0.00001 = 318.30 ohms

1

2 X 3.1415 X 50 X 0.00002 = 159.15 ohms

1 + 1

318.30 159.15 = 106.1 ohms

Answer total capacitance reactance 106.1 ohms

Hope this makes sense CJS

 

[springcrocus]

Have a look HERE for the various relationships (reactance, inductance etc.)