Lost energy when capacitor discharges

In summary, the conversation discusses the energy loss in a system consisting of two capacitors: a 1-Farad capacitor A and a 9-Farad capacitor B. The system is initially in state (a) where A is charged with 1 Coulomb of charges, and then it is connected in parallel with B in state (b), resulting in the discharge of A. The question is raised about where the energy goes during this process. The equations Q=C\phi and U=(1/2)C\phi^2 are referenced in finding the total energy. The expert concludes that the energy is lost as heat due to resistance in the setup and also as electromagnetic radiation due to the oscillating current flow.
  • #1
Tekk
9
0

Homework Statement


[/B]
I have two capacitors: 1-Farad capacitor A, and 9-Farad capacitor B.
In state (a), I charged A with 1 Coulomb of charges, as depicted in figure (a).
In state (b), I paralleled A with B, by doing this I discharged A, as depicted in figure (b).

I try to find the total energy of state (a) and state (b). From what I have calculated, the system lost 90% of its energy when it goes from (a) to (b). Where does the energy go?

Homework Equations



[itex]Q=C\phi[/itex]
[itex]U=(1/2)C\phi^2[/itex]

The Attempt at a Solution


[/B]
Please refer to the image below.
IMG_0050 copy.jpg
 
Last edited:
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  • #2
Tekk said:
Where does the energy go?
You heat the wires and the capacitors from the resistances in the setup. A tiny bit is also lost to electromagnetic radiation.
 
  • #3
mfb said:
You heat the wires and the capacitors from the resistances in the setup. A tiny bit is also lost to electromagnetic radiation.

I think my approach to find energy assumes there is no resistance on wires. So I suspect that energy would not turn to heat on these wires.

What I see during the discharge process is a flow of electrons. Can you explain how electromagnetic radiation is produced?
 
  • #4
Your approach is independent of the resistance.
Connecting capacitors like that without any resistors is a very special case, it will give you an extremely good oscillator (as you always have a small inductance) and all the lost energy will be emitted as radiation over time.
Tekk said:
Can you explain how electromagnetic radiation is produced?
You have a variable current flow = accelerated charges. With small resistances, current will oscillate back and forth for a while.
 

What is a capacitor?

A capacitor is an electronic component that stores electrical energy in the form of an electric field. It is made up of two conductive plates separated by an insulating material called a dielectric.

What happens when a capacitor discharges?

When a capacitor discharges, the stored energy is released in the form of an electric current. This current flows from one plate of the capacitor to the other, until the capacitor is completely discharged.

Why is energy lost when a capacitor discharges?

Energy is lost when a capacitor discharges due to the presence of resistance in the circuit. This resistance converts some of the electrical energy into heat, causing a decrease in the overall energy level of the capacitor.

How can the lost energy from a capacitor discharge be minimized?

The lost energy from a capacitor discharge can be minimized by using a low-resistance circuit, such as a superconductor, to allow for a more efficient flow of electricity. Additionally, using capacitors with a higher capacitance value can also help reduce energy loss.

Can the lost energy from a capacitor discharge be recovered?

Technically, the lost energy from a capacitor discharge cannot be recovered. However, the discharged capacitor can be recharged by applying an external voltage, thereby restoring its energy level to its original value. This process can be repeated multiple times, effectively reusing the energy stored in the capacitor.

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