All Questions
12
questions
0
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1
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132
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Different result when deriving electric force as $dW/dr$ and $-dU/dr$
Work done by electric field, $W$ is the negative of the change in electric potential energy, $U_r$.
$$W=-\Delta U$$
By considering an infinitesimal change in EPE, we can deduce that electric force, $...
- 113
2
votes
2
answers
174
views
I really don't understand the sign Work and energy in an electric field
This might be a super simple question to answer but I can't find one that makes sense to me and I feel like I am getting conflicting answers. I have always thought that positive work means that the ...
- 23
0
votes
6
answers
3k
views
WHY is there a negative sign in the formula of potential gradient?
Before you tell me there are a bunch of other similar questions asked as well, hear me out ;(
I'm really confused when it comes to work being done. When you're considering a charge moving from a one ...
0
votes
1
answer
526
views
How is the reference point of potential energy defined in electric fields?
Consider the diagram below of a positive charge and three points marked in the field X, Y and Z.
I understand that for a gravitational field, we define the potential energy as being always negative, ...
- 323
0
votes
2
answers
219
views
Why is there no negative sign in the formula of work against electric field?
Why is there no negative sign in the first formula of work done against electric field where as second formula below has it?
- 45
4
votes
2
answers
24k
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When work done is taken negative in electrostatics?
Let us say a point charge Q was moved across a potential difference V, then work done would be : QV.
This work is taken negative when done external agent, Please explain when It is negative and ...
3
votes
3
answers
5k
views
Why is there a minus in the definition of the electric potential?
We usually say that the work done by a force is $\mathrm{d}W = F\cdot\mathrm{d}l$, and the electric potential is $\mathrm{d}U = -E \cdot \mathrm{d}l$). Why do we put a negative sign over there? Is it ...
1
vote
1
answer
8k
views
Why does the electric potential for an infinite line charge seem to have to be worked out from negative infinity rather than positive infinity?
The electric field of an infinite line charge in the plane perpendicular to the line charge can be given as:
$$E=\frac{1}{2\pi \epsilon r}$$
Where $r$ is the perpendicular distance from the line.
...
- 176
0
votes
2
answers
2k
views
Convention of potential energy in dipole and the conservation of energy
As I understand it, the convention for the potential energy of a dipole in a uniform electric field has the following zero point:
$U(\pi/2)=0$
I understand how this makes the calculation easier to ...
- 1
6
votes
4
answers
169k
views
Relation between Electric field and potential
I am unable to understand from this - sign comes. Which step I have done wrong?
- 135
2
votes
2
answers
10k
views
Electric field for concentric spheres
I have a couple clarifying questions:
(A) in $E=kq/r^2$ for the area between a sphere inside another spherical shell, the sphere inside is considered a point charge. However, the sphere inside has a ...
- 89
0
votes
1
answer
2k
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Which is the right sign convention for the potential difference?
The circulation of the electric field gives the potential difference, but is it :
$$V_B-V_A = \int_A^B\vec{E}.\vec{dOM} \hspace{1.5cm} (1)$$
or
$$V_B-V_A = - \int_A^B\vec{E}.\vec{dOM} \hspace{1cm} (...
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