Several 0.25-muF capacitors are available. The voltage across each is not to exc

Question

Several 0.25-muF capacitors are available. The voltage across each is not to exceed 600 V. You need to make a capacitor with capacitance 0.25 muF to be connected across a potential difference of 960 V. (a) Show in a diagram how an equivalent capacitor with the desired properties can be obtained. (b) No dielectric is a perfect insulator that would not permit the flow of any charge through its volume. Suppose that the dielectric in one of the capacitors in your diagram is a moderately good conductor. What will happen in this case when your combination of capacitors is connected across the 960-V potential difference?

Explanation / Answer

a) when capacitors are connected in series, if capaictance are C1 and C2, then net capacitance is given by C1*C2/(C1+C2)

when capacitors are connected in parallel, net capacitance is given by C1+C2.

when capacitors are in series, voltage is divided between them

when capacitors are connected in parallel, voltage is same across all of them

keeping above 4 points in mind,

first lets see how we can bring down 960 volts so that the safe voltage level of each capacitor is not exceeded.

if we connect two capacitors in series, 960 volts will be divided as 480 volts and 480 volts among the two capacitors and hence as it is below 600 volts level, we can achieve our task

but if we connect two 0.25 uF in series, net capacitance will be 0.125 uF.

so we need two 0.5 uF capacitors in series , so that net capacitance will be 0.25 uF.

to get 0.5 uF out of 0.25 uF capacitors, we can connect 2 of them in parallel.

so the final conenction is as below:

2 0.25 uF capacitors in parallel. this is set 1.
2 0.25 uF capacitors in parallel. this is set 2.

finally, set 1 and set 2 are in series.

so in the end, we get 480 volts across all the capacitors, well below the 600 volts level and we get 0.25 uF total capacitance.

part b:
as a dielectric increases the capacitance by its dielectric constant, if any dielectric is present, the capacitance will increase and we wont be able to achive our desired 0.25 uF level with the previous setting.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.