Problem about electric potential and power transmitted down a cable

  • Thread starter Another
  • Start date
  • #1
101
5
8.png
9.png
7.png


When to use ## V =-\int E ⋅ dl ## or ## V =\int E ⋅ dl ## ?

When i use ## V =-\int E ⋅ dl ##. i can not show that P = IV because ##\frac{ln \frac{b}{a}}{ln \frac{a}{b}} ≠ 1##

But the solution use ## V =\int E ⋅ dl ## I'm concerned about using "minus" .
 

Attachments

  • 7.png
    7.png
    119 KB · Views: 608
  • 8.png
    8.png
    12.1 KB · Views: 584
  • 9.png
    9.png
    31.7 KB · Views: 534

Answers and Replies

  • #2
vela
Staff Emeritus
Science Advisor
Homework Helper
Education Advisor
15,473
2,113
The notation in the solutions is kind of sloppy, but it's easy enough to understand what was meant.

Assume that ##\vec E## points radially outward. Then the inner conductor is at a higher potential than the outer conductor so that ##V = V_a - V_b##. So you have
$$V = V_a - V_b = -\int_b^a \vec E \cdot d\vec l = \int_a^b \vec E \cdot d \vec l.$$
 

Related Threads on Problem about electric potential and power transmitted down a cable

Replies
4
Views
2K
Replies
1
Views
14K
Replies
2
Views
14K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
2K
Replies
8
Views
11K
  • Last Post
Replies
5
Views
6K
Replies
7
Views
2K
Top