What is the energy stored in the capacitor?

  • Thread starter Thread starter donjt81
  • Start date Start date
  • Tags Tags
    Capacitor Energy
AI Thread Summary
The discussion centers on calculating the energy stored in a capacitor, with an initial query about 20 J being placed across a 15µF capacitor. It is suggested that the correct interpretation should be 20 volts instead of 20 joules. The energy stored in the capacitor is confirmed to be 20 J if that amount is indeed added, as no energy is lost due to resistance. The method for calculating energy involves integrating the voltage over the charge, with voltage increasing from 0 to 20 V as the capacitor charges. The conversation emphasizes the relationship between voltage and charge in determining the energy stored.
donjt81
Messages
70
Reaction score
0
20 J is placed across a 15uF capacitor. What is the energy stored in the capacitor?

any ideas on how to do this?
 
Physics news on Phys.org
donjt81 said:
20 J is placed across a 15uF capacitor. What is the energy stored in the capacitor?

any ideas on how to do this?
Check the question. I think it should be 20 volts not 20 J. (If 20 J is added to the capacitor, the energy stored in the capacitor is 20 J. because there is no energy is lost due to resistance).

The energy is \int_0^q Vdq where V = potential (energy/charge) between the plates of the capacitor. It is 0 Volts initially but increases to 20 V. when fully charged.

Use the relationship between V and Q in a capacitor to express dq in terms of dV and then integrate with respect to V over the range 0 to 20 V.

AM
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Struggle to understand the concept of the question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »

Similar threads

LC oscillations - two capacitors and an inductor
Replies
15
Views
589
Capacitance of a parallel plate capacitor with a metal plate kept inside
Replies
11
Views
3K
Calculations involving different Dielectrics and Capacitors
Replies
7
Views
2K
Calculating the voltage across capacitors and resistors with switches
Replies
2
Views
774
Finding charge on a capacitor given potential difference across two points
Replies
4
Views
2K
Comparing energy lost by the battery & energy gained by the capacitor.
Replies
5
Views
2K
Ranking charge stored on three capacitors by a battery
Replies
6
Views
3K
Capacitor Questions Charging and Discharging
Replies
4
Views
3K
Determining Inductance L in an LC Circuit
Replies
5
Views
2K
Why Capacitors in Parallels vs. Series: Coaxial Capacitor Case
Replies
2
Views
2K

Hot Threads

Recent Insights

Back
Top