Some help with capacitors please

  • Thread starter christianerik
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    Capacitors
In summary, the conversation discusses a problem involving a closed switch, an uncharged capacitor, and various values of resistance, current, and voltage. It advises to use the equation C=Q/V and suggests finding the voltage between the resistance by subtracting it from the given voltage, then using the equation to solve for the charge on the capacitor. It also recommends showing effort and using the homework template when seeking help on a forum.
  • #1
christianerik
9
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At t=0 the switch S is closed with the capacitor is uncharged.

..... 3M ohm... 102 micro F
--------------^^^^^--------ll-------------
l l
l ... s...<----i--->......l
l-------l i-------/.--------------------------l
17 V

What is the charge on the capacitor when
I = 2 mA? Answer in units of C.

Need some help understanding it...
 
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  • #2
hello christianerik, welcome to PF

you know that C=Q/V

find the voltage between the resistance using the given values of current and resistance [since it’s connected in series with the capacitor, you should subtract this value from 17 volts to get the voltage between the capacitor plates]. then use the previous equation to solve.
 
  • #3
christianerik, welcome to PF Forums! You will find many useful discussions and people willing to help you. Before we can do so, you need to show your own effort towards solving your problem. You may want to reread this https://www.physicsforums.com/showthread.php?t=94380" that is shown at the top of this topic. If you don't have a clue, start by stating all that you understand about your problem and lead us to the point where you are stuck.

Using the homework template that is given, when you initiate a thread, is also helpful no only to us but it also helps you organize the question more clearly. Some good examples of homework threads may be viewed https://www.physicsforums.com/showthread.php?t=131568".
 
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  • #4
Your drawing's not clear. I suggest sketching on paper, or using drawing software and uploading the image. Also recommend double-checking the values in your question, particularly for the resistor & current.
 
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1. What is a capacitor and how does it work?

A capacitor is an electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied across the plates, one plate becomes positively charged and the other becomes negatively charged. This creates an electric field between the plates, which stores the electrical energy.

2. What are the different types of capacitors?

There are several types of capacitors, including ceramic capacitors, electrolytic capacitors, film capacitors, and variable capacitors. Each type has different properties and is used for specific purposes. For example, ceramic capacitors are small and inexpensive, while electrolytic capacitors have a high capacitance and are often used in power supply circuits.

3. How do I choose the right capacitor for my circuit?

The type of capacitor you choose will depend on the requirements of your circuit. Factors to consider include the capacitance, voltage rating, and frequency response. It's important to consult the datasheet for the capacitor to ensure it meets the specifications of your circuit.

4. Can capacitors be used to store energy?

Yes, capacitors can store electrical energy. However, they are not as efficient as batteries for long-term energy storage. Capacitors are often used for short-term energy storage in electronic devices, such as cameras and flashlights.

5. What are some common problems with capacitors?

One common problem with capacitors is leakage, where the capacitor loses its charge over time. This can be caused by defects in the dielectric material or high temperatures. Another issue is breakdown, where the electric field between the plates becomes too strong and can damage the capacitor. Proper selection and usage of capacitors can help avoid these problems.

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