Finding potential at a point in capacitor

In summary, the conversation discusses using Kirchhoff's law to solve for the current value and Ohm's law to calculate the voltage at point a. It also presents a question about which resistance and capacitance values to use in calculations.
  • #1
Sunwoo Bae
60
4
Homework Statement
shown below
Relevant Equations
Ohm's law, Kirchhoff law,
1644237234303.png


I tried solving the part (a), and got I =1.82 A for the current value using Kirchoff's law.
Next, I want to use Ohm's law to calculate the voltage at point a.
Va = IR
In this equation, will resistance R correspond to 4.4Ω or 8.8Ω?
How do you determine which resistance to use when solving this problem?

As for part B, I was able to calculate Ceq and Q through following works:
1644242333552.png


I am now trying to find the potential at point b with the switch open through equation
Vb = Q/c
Again, which value of capacitance, 0.48 µF or 0.36 µF, and why?

Thank you!
 
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  • #2
Have you come across the idea of a potential divider? The voltage across either resistors is in proportion to the value of the resistance. The same idea carries across for the capacitors, except the weights are the reciprocals ##1/C##. Can you show why this is true?
 
  • #3
Sunwoo Bae said:
Homework Statement:: shown below
Relevant Equations:: Ohm's law, Kirchhoff law,

View attachment 296733

I tried solving the part (a), and got I =1.82 A for the current value using Kirchoff's law.
Next, I want to use Ohm's law to calculate the voltage at point a.
Va = IR
In this equation, will resistance R correspond to 4.4Ω or 8.8Ω?
How do you determine which resistance to use when solving this problem?

As for part B, I was able to calculate Ceq and Q through following works:
View attachment 296735

I am now trying to find the potential at point b with the switch open through equation
Vb = Q/c
Again, which value of capacitance, 0.48 µF or 0.36 µF, and why?

Thank you!
You can use either resistor value.

You can use either capacitor value.

The problem states to use a potential value of 0 V at the negative terminal of the source.
What is the potential value at the positive terminal?
 

1. What is potential at a point in a capacitor?

The potential at a point in a capacitor refers to the amount of electric potential energy per unit charge at that specific point. It is a measure of the electric field strength at that point, and is typically measured in volts (V).

2. How is potential at a point in a capacitor calculated?

The potential at a point in a capacitor can be calculated using the equation V = Q/C, where V is the potential, Q is the charge stored in the capacitor, and C is the capacitance of the capacitor. This equation is based on the relationship between potential, charge, and capacitance in a capacitor.

3. What factors affect the potential at a point in a capacitor?

The potential at a point in a capacitor is affected by the amount of charge stored in the capacitor, the distance between the plates, and the material between the plates. The potential can also be affected by the presence of other charges or external electric fields.

4. How does potential at a point in a capacitor relate to the electric field?

The potential at a point in a capacitor is directly related to the electric field at that point. The electric field is a measure of the force per unit charge, and the potential is a measure of the energy per unit charge. Therefore, the electric field is the gradient of the potential, or the rate of change of potential with respect to distance.

5. How does potential at a point in a capacitor change over time?

The potential at a point in a capacitor can change over time as the charge stored in the capacitor changes. When the capacitor is charging, the potential at a point will increase as more charge is stored. When the capacitor is discharging, the potential at a point will decrease as charge is released. The rate at which the potential changes over time is determined by the capacitance of the capacitor and the amount of current flowing through it.

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