What is the steady state voltage across the capacitor in this open circuit?

In summary, The problem asks to find the steady state voltage across the capacitor. The circuit has a gap, which is supposed to be bridged by a switch. The diode used to be where the gap is, but the voltage source's orientation causes it to become a gap. In steady state, the capacitor behaves as an open and no current flows through the 2 branches, resulting in a voltage drop of 0V across the resistors. This means that the ends of the capacitor are at the same voltage (V_dc), making the voltage difference 0V. Therefore, the answer is a) 0V. If the capacitor was not in steady state, its voltage would also be 0V since initially it behaves as
  • #1
pyroknife
613
3
The problem asks to find the steady state voltage across the capacitor. i attached the circuit (sorry for the poorly drawn and yes, that open part of the branch is supposed to be there) This is a multiple choice question where the answers are:
a) 0V
b) V_dc/2
c) V_dc/3
d) V_dc
e) 2*V_dc

In steady state, a capacitor behaves as an open.
If the capacitor was placed before the resistors, I think its voltage would be V_dc.
However, this capacitor is placed after the resistor.
In steady state, no current will flow through these 2 branches due to the open circuit, thus the voltage drop across the 2 resistors are 0.
This means that the ends of the capacitor are at the same voltage (V_dc). Thus the voltage difference is V_dc-V_dc=0.
So the answer is a. Am I right?
 

Attachments

  • Circuit.png
    Circuit.png
    893 bytes · Views: 397
Physics news on Phys.org
  • #2
pyroknife said:
The problem asks to find the steady state voltage across the capacitor. i attached the circuit (sorry for the poorly drawn and yes, that open part of the branch is supposed to be there)
I expect that gap is supposed to be bridged by a switch, otherwise the circuit is rather pointless.
 
  • #3
NascentOxygen said:
I expect that gap is supposed to be bridged by a switch, otherwise the circuit is rather pointless.

The diode used to be where the gap is. But the orientation of the voltage source implies that the diode will become a gap because it will be reverse biased.
 
  • #4
The capacitor (if it carries any charge) will discharge via the resistor path, until the capacitor voltage reaches zero.
 
  • #5
NascentOxygen said:
The capacitor (if it carries any charge) will discharge via the resistor path, until the capacitor voltage reaches zero.

Yes. So I think my proof in my first post was correct.

Just for practice, if this was not steady state and the capacitor just began to charge, would its voltage be 0 still? I think that because initially when (time is just greater than 0) a capacitor behaves as a short branch.
 
  • #6
pyroknife said:
Just for practice, if this was not steady state and the capacitor just began to charge, would its voltage be 0 still? I think that because initially when (time is just greater than 0) a capacitor behaves as a short branch.
Yes, but not for that reason. To change the voltage on a capacitor you have to add charge to it. Adding charge takes time. Immediately after t=0 there has been no time to add much charge, so the voltage across the capacitor plates hasn't changed.
 

1. What is an open circuit with capacitor?

An open circuit with capacitor refers to a circuit where the capacitor is not connected to a complete path for the current to flow. This means that there is a gap or break in the circuit which prevents the flow of electricity.

2. How does an open circuit with capacitor work?

In an open circuit with capacitor, the capacitor is not connected to a power source or load. This allows the capacitor to store an electric charge, creating an electric field between its plates. When the circuit is closed, the capacitor discharges its stored energy, allowing the current to flow through the circuit.

3. What is the purpose of an open circuit with capacitor?

An open circuit with capacitor can be used for various purposes, such as filtering out specific frequencies in electronic circuits, storing electric charge for use in electronic devices, or as a voltage regulator to maintain a constant voltage in a circuit.

4. What are the advantages of using an open circuit with capacitor?

Some advantages of using an open circuit with capacitor include its ability to store energy and release it quickly, its small size and lightweight compared to other components, and its ability to filter out unwanted frequencies in a circuit.

5. What are the potential drawbacks of an open circuit with capacitor?

One potential drawback of using an open circuit with capacitor is that it can be affected by external factors such as temperature and humidity, which can alter its capacitance and performance. In addition, if the capacitor is not properly discharged or handled, it can cause electric shocks or damage to electronic devices.

Similar threads

  • Introductory Physics Homework Help
Replies
2
Views
487
  • Introductory Physics Homework Help
Replies
3
Views
567
  • Introductory Physics Homework Help
Replies
20
Views
1K
Replies
3
Views
381
  • Introductory Physics Homework Help
Replies
4
Views
348
  • Introductory Physics Homework Help
Replies
3
Views
538
  • Introductory Physics Homework Help
Replies
14
Views
612
  • Introductory Physics Homework Help
Replies
6
Views
73
  • Introductory Physics Homework Help
Replies
15
Views
1K
  • Introductory Physics Homework Help
Replies
10
Views
1K
Back
Top