To double the energy stored by a capacitor, you should:

  • Thread starter Pi Face
  • Start date
  • #1
76
0
a) double the voltage
b) double the capacitance

WIth the equation U=(1/2)CV^2 doubling the voltage quadruples U and doubling the capacitance doubles U.

However if you double the capacitance in the expression (1/2)Q^2/C you half U instead.

Also, doubling the voltage doubles U in the equation (1/2)QV

So what's the reasoning behind this and where am I confusing myself?
 

Answers and Replies

  • #2
gneill
Mentor
20,925
2,867
a) double the voltage
b) double the capacitance

WIth the equation U=(1/2)CV^2 doubling the voltage quadruples U and doubling the capacitance doubles U.

However if you double the capacitance in the expression (1/2)Q^2/C you half U instead.

Also, doubling the voltage doubles U in the equation (1/2)QV

So what's the reasoning behind this and where am I confusing myself?

Yeah, it's a bit tricky because each of the expressions for energy has behind it certain implications about what is varying and what remains constant. Just because a variable doesn't appear in the expression doesn't mean it doesn't change or have an impact. You have to think of the implied physical scenario when you 'wiggle' the variables in a given equation.

For a given capacitor Q = C*V always holds and specifies the effect on the "unseen" variable. So if you muck with one of the variables and hold another constant then by implication the third must change too.
 

Related Threads on To double the energy stored by a capacitor, you should:

  • Last Post
Replies
4
Views
2K
  • Last Post
Replies
3
Views
12K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
1
Views
4K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
12
Views
525
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
5
Views
689
Top