All Questions
Tagged with conventions coulombs-law
13
questions
-1
votes
1
answer
88
views
Why did we choose Coulomb's constant $k$ as $9\cdot10^9 \rm Nm^2/C^2$ while define unit of charge instead of any other number?
I understand that while defining charge, Coulomb had to choose any arbitrary value of $k$ to describe unit of charge. But, why did we chose $9\cdot10^9 \rm Nm^2/C^2$ as the value of $k$, but not any ...
- 17
0
votes
4
answers
98
views
What is the direction of $\vec r_{21}$ (position vector)? towards $\vec r_{2}$ or towards $\vec r_{1}$?
The vector representation of Coulomb's law uses a vector between the position vectors of the charges at rest. However, my teacher and a few books use the convention that vector $\vec r_{21} = \vec r_1 ...
2
votes
3
answers
224
views
Why gravitational constant $G$ does not have the factor of $4π$?
We know that electrostatic constant $K=\frac{1}{4\pi\epsilon}$.
This $4\pi$ came from the surface area of the surface in which charge is enclosed.
Then, why don't gravitational constant has the factor ...
- 21
2
votes
6
answers
1k
views
If protons were negative and electrons were positive, would Coulomb's Law change?
Coulomb's Law is $$F=k\frac{q_1 q_2}{r^2}$$
where $F$ is the force, $k$ is the Coulomb's universal constant, $q_1$ and $q_2$ are the charges, and $r$ is the distance between the two charges.
- 595
0
votes
1
answer
59
views
Confusion In Derivative of Electrostatic Potential Energy Of 2 Charge System
In my textbook, the derivative shows a -ve sign in front of the integral.
My confusion is why is that -ve sign there?
Isn't the direction of external force and displacement the same and hence shouldn'...
- 33
6
votes
1
answer
185
views
Why is the constant in Coulomb's law written in terms of $\pi$ but not the constant in Gravitation?
What is the significance of writing it as $\frac{1}{4\pi \epsilon _0}$? Why not just name the whole thing $\epsilon _0$? And if there is a significance, why not do the same thing for gravitation?
I ...
- 6,355
1
vote
2
answers
1k
views
Why is the electric potential at a distance of $R$ from a point charge $q$ equal to $\frac{-q}{4\pi\varepsilon_0 R}$
My textbook mentions that the electric potential at distance of $R$ from a point charge $q$ will be given by $\dfrac{-q}{4\pi\varepsilon_0 R}$. I don't understand why the negative symbol appears here.
...
- 727
0
votes
2
answers
4k
views
Electric field and test charge
I have a question about the definition of electric field. Texts define it as the force on on a positive test charge ($q_0$), divided by the charge on the positive test charge.
$$ E = k \frac{...
- 1,548
0
votes
2
answers
4k
views
Is electric potential energy measured in absolute value?
Is the formula for electric potential energy ($U = kqQ/r$) measured in absolute value? In other words, as the magnitude of $U$ increases, does electric potential energy increases too? For example, if $...
- 75
2
votes
2
answers
977
views
Why are the electric and magnetic constants where they are?
$ε_0$, the electric permittivity and $μ_0$, the magnetic magnetic permeability were introduced in Coulomb's Constant and Ampere's Constant in order to make units and magnitudes match, in Coulomb's ...
- 353
4
votes
4
answers
3k
views
Sign in vector equation for electrostatic Coulomb force
In the vector equation for the electrostatic force:
$$\vec{F} = \frac{1}{4\pi\epsilon_{0}}\cdot\frac{q_1\cdot q_2}{r^2}\cdot \hat{r} \tag{1}$$
Is the absolute value of $q_1$ and $q_2$ taken? As $(1)$...
- 283
2
votes
3
answers
1k
views
Why is the electric potential of a point from a point charge of +Q positive?
According to the formula, $$V = - \int \vec E \cdot d\vec r.$$
The electric potential of a point charge is $\frac{KQ}R$? However, when I perform the integration, my answer is $-\frac{KQ}R$.
Since ...
- 1,325
-1
votes
3
answers
16k
views
Direction of electric field lines and electrostatic force
Direction of electric field and electrostatic force should be same by the equation
$$\vec{F} = \frac{k q q_0}{r^2}$$
Electric Field $$\vec{E} = \frac{k q}{r^2}$$
Let us suppose that there is a ...
- 1,426