- #1
- 1,402
- 3
My colleague and I have a disagreement about the storage of electrical energy using capacitors in DC circuitry. It all has to do with the equation for the capacitive energy storage, namely the energy stored in a capacitor with capacitance C charged from a power supply at some constant potential V is given by:
E=0.5*CV2
This represents half of the energy drawn from the power supply during charging, with the other half being "used up" as the charging energy. In other words, E=CV2 is drawn from the power supply, but only half of it ends up stored in the capacitor. I have never been able to find a detailed description of where the energy used in charging the capacitor goes. One website I found mentioned something about "resistive losses in the wires", but that doesn't seem correct to me.
Anyway, I have (at least) two questions about this system (assuming I haven't made a mistake in the above description):
1) what is the mechanism by which the charging energy is "used up"?
2) When you try to recover the stored energy from the capacitor by discharging it, are those same loss mechanisms in place? In other words, if I wanted to use the stored energy to power a device, would I be able to extract the entire 0.5*CV2 stored in the charged capacitor, or would I again lose half upon discharging? Does the answer depend on how the capacitor is coupled to the circuit when it is discharged?
Thanks in advance for assistance.
E=0.5*CV2
This represents half of the energy drawn from the power supply during charging, with the other half being "used up" as the charging energy. In other words, E=CV2 is drawn from the power supply, but only half of it ends up stored in the capacitor. I have never been able to find a detailed description of where the energy used in charging the capacitor goes. One website I found mentioned something about "resistive losses in the wires", but that doesn't seem correct to me.
Anyway, I have (at least) two questions about this system (assuming I haven't made a mistake in the above description):
1) what is the mechanism by which the charging energy is "used up"?
2) When you try to recover the stored energy from the capacitor by discharging it, are those same loss mechanisms in place? In other words, if I wanted to use the stored energy to power a device, would I be able to extract the entire 0.5*CV2 stored in the charged capacitor, or would I again lose half upon discharging? Does the answer depend on how the capacitor is coupled to the circuit when it is discharged?
Thanks in advance for assistance.