The ratio of coulomb's electrostatic force to the gravitational force between an electron and a proton separated by some distance is $$2.4\times 10^{39}$$. The ratio of the proportionality constant, $$K=\frac{1}{4\pi\varepsilon_0}$$ to the gravitational constant $$G$$ is nearly:
(Given that the charge of the proton and electron each $$=1.6\times 10^{-19}$$, the mass of the electron = $$9.11\times 10^{-31}$$ kg, the mass of the proton $$=1.67\times 10^{-27}$$ kg):
 1 $$10^{20}$$ 2 $$10^{30}$$ 3 $$10^{40}$$ 4 $$10$$
Subtopic:  Coulomb's Law |
60%
From NCERT
NEET - 2022
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The acceleration of an electron due to the mutual attraction between the electron and a proton when they are $$1.6~\mathring{A}$$ apart is:
$$\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9~ \text{Nm}^2 \text{C}^{-2}$$ )

 1 $$10^{24} ~\text{m/s}^2$$ 2 $$10^{23} ~\text{m/s}^2$$ 3 $$10^{22}~\text{m/s}^2$$ 4 $$10^{25} ~\text{m/s}^2$$
Subtopic:  Coulomb's Law |
75%
From NCERT
NEET - 2020
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Two point charges $$A$$ and $$B$$, having charges $$+Q$$ and $$-Q$$ respectively, are placed at a certain distance apart and the force acting between them is $$F.$$ If $$25\%$$ charge of $$A$$ is transferred to $$B$$, then the force between the charges becomes:

 1 $$\frac{4F}{3}$$ 2 $$F$$ 3 $$\frac{9F}{16}$$ 4 $$\frac{16F}{9}$$
Subtopic:  Coulomb's Law |
76%
From NCERT
NEET - 2019
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Suppose the charge of a proton and an electron differ slightly. One of them is $$-e$$, the other is ($$e+\Delta e$$). If the net of electrostatic force and gravitational force between two hydrogen atoms placed at a distance $$d$$ (much greater than atomic size) apart is zero, then $$\Delta e$$ is of the order of? (Given mass of hydrogen ${\mathrm{}}_{}$$$m_h = 1.67\times 10^{-27}~\text{kg}$$)
1. $$10^{-23}~\text{C}$$
2. $$10^{-37}~\text{C}$$
3. $$10^{-47}~\text{C}$$
4. $$10^{-20}~\text{C}$$

Subtopic:  Coulomb's Law |
65%
From NCERT
NEET - 2017
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Two identical charged spheres suspended from a common point by two massless strings of lengths $$l,$$ are initially at a distance $$d$$ $$\left ( d\ll l \right )$$ apart because of their mutual repulsion. The charges begin to leak from both the spheres at a constant rate. As a result, the spheres approach each other with a velocity $$v.$$ Then, $$v$$ varies as a function of the distance $$x$$ between the sphere, as:
1. $$v\propto x$$
2. $$v\propto x^{-1/2}$$
3. $$v\propto x^{-1}$$
4. $$v\propto x^{1/2}$$
Subtopic:  Coulomb's Law |
78%
From NCERT
NEET - 2016
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Two pith balls carrying equal charges are suspended from a common point by strings of equal length, the equilibrium separation between them is $$r$$ (as shown in Fig. I). Now, as shown in Fig. II, the strings are rigidly clamped at half the height. The equilibrium separation between the balls now becomes:

1. $$\frac{r}{\sqrt[3]{2}}$$
2. $$\frac{r}{\sqrt[2]{2}}$$
3. $$\frac{2r}{3}$$
4. none of the above

Subtopic:  Coulomb's Law |
70%
From NCERT
AIPMT - 2013
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Two positive ions, each carrying a charge q, are separated by a distance d. If F is the force of repulsion between the ions, the number of electrons missing from each ion will be:
(e is the charge on an electron)

1. $\frac{4\pi {\epsilon }_{0}F{d}^{2}}{{e}^{2}}$

2. $\sqrt{\frac{4\pi {\epsilon }_{0}F{d}^{2}}{{d}^{2}}}$

3. $\sqrt{\frac{4\pi {\epsilon }_{0}F{d}^{2}}{{e}^{2}}}$

4. $\frac{4\pi {\epsilon }_{0}F{d}^{2}}{{q}^{2}}$

Subtopic:  Coulomb's Law |
77%
From NCERT
AIPMT - 2010
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The unit of permittivity of free space ε0 is:

 1 Newton metre2 / Coulomb2 2 Coulomb2 /Newton metre2 3 Coulomb2/ (Newton metre)2 4 Coulomb/Newton metre

Subtopic:  Coulomb's Law |
72%
From NCERT
AIPMT - 2004
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