Two capacitors connected in series

  • Thread starter Thread starter songoku
  • Start date Start date
  • Tags Tags
    Capacitors Series
Click For Summary
SUMMARY

The discussion centers on the analysis of two capacitors, with capacitances of 30 μF and 60 μF, each initially charged to 50 μC and 70 μC, respectively, when connected in series. It is established that in a series configuration, the charge on each capacitor must be the same, leading to the conclusion that the initial charges are irrelevant once connected. The final potential differences across the capacitors are calculated to be 5/3 V and 7/6 V, indicating that none of the provided multiple-choice answers are correct.

PREREQUISITES
  • Understanding of capacitance and its units (μF)
  • Knowledge of charge (μC) and voltage relationships in capacitors
  • Familiarity with series and parallel circuit configurations
  • Basic grasp of the formula Q = CV (Charge = Capacitance x Voltage)
NEXT STEPS
  • Study the principles of series and parallel circuits in capacitor configurations
  • Learn how to calculate equivalent capacitance in series and parallel arrangements
  • Explore the implications of charge conservation in electrical circuits
  • Investigate the effects of initial charge on capacitors when connected in different configurations
USEFUL FOR

Students studying electrical engineering, physics enthusiasts, and anyone seeking to understand capacitor behavior in series circuits.

songoku
Messages
2,509
Reaction score
393

Homework Statement


Two capacitors, capacitance of 30 μF and 60 μF respectively, each has charge of 50 μF and 70 μF. The capacitors then connected in series. Find the potential difference on each capacitor now


Homework Equations


Q = CV


The Attempt at a Solution


I know that the charge should be same for series circuit but I don't know how to analyse this question. Each capacitors has its own charge and voltage and after connected in series, their charge should be the same. How to find it?
 
Physics news on Phys.org
songoku said:
... each has charge of 50 μF and 70 μF?

uF is a measure of capacitance, not charge, so I don't understand what you are saying here.
 
Think about what "The capacitors then connected in series" means. Presumably only one plate of each is connected together otherwise they would be in parallel. If only one side of each capacitor is connected together how much current can flow?
 
phinds said:
uF is a measure of capacitance, not charge, so I don't understand what you are saying here.

sorry, I meant 50 μC and 70 μC

CWatters said:
Think about what "The capacitors then connected in series" means. Presumably only one plate of each is connected together otherwise they would be in parallel. If only one side of each capacitor is connected together how much current can flow?

Sorry I really don't know the concept here of how to determine the current when only one side of each capacitor is connected...I assume that one positive plate is connected to other negative plate. Will the case be the same if the series circuit connects positive plate to positive plate?

Thanks
 
If the only one end of each capacitor is connected to anything there is no closed circuit so no current flow. Therefore the capacitors retain whatever charge and voltage they had before they were connected.
 
CWatters said:
If the only one end of each capacitor is connected to anything there is no closed circuit so no current flow. Therefore the capacitors retain whatever charge and voltage they had before they were connected.

Sorry, actually there are choices for this question:
a. 4 and 8 Volt
b. 8 and 4 Volt
c. 5 and 5 Volt
d. 3 and 6 Volt
e. 6 and 3 Volt

If the capacitors retain their voltage, their voltage should be 5/3 and 7/6 Volt.

So there is no correct choice?

Thanks
 

Similar threads

Replies
20
Views
2K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 4 ·
Replies
4
Views
4K
Replies
4
Views
2K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 14 ·
Replies
14
Views
1K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
5
Views
726
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 18 ·
Replies
18
Views
3K