Question

Two 6µF capacitance are connected in series with one having a capacitance of 12µF.Find the total equivalent circuit capacitance. What capacitance must be added in series to obtain a capacitance of 1.2µF.

Answer 1

When three capacitors are connected in series, the equivalent capacitance will be

$$C=\frac{1}{1/C_1+1/C_2+1/C_3}=\\ \space\\ =\frac{1}{1/6+1/6+1/12}=2.4\space\mu\text{F}.$$

Now solve another problem, that is, find what capacitance must be added in series if the total capacitance is 1.2 µF:

$$1.2=\frac{1}{1/2.4+1/C_x},\\ \space\\ C_x=\frac{1}{1/1.2-1/2.4}=2.4\space\text{µF}.$$