capacitor question

[donjt81]

20 J is placed across a 15uF capacitor. What is the energy stored in the capacitor?

any ideas on how to do this?

[Andrew Mason]

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