A metal cube of a side \(5~\text{cm},\) is charged with \(6~\text{μC.}\) The surface charge density on the cube, is:
1. \(0.125\times10^{-3}~\text{C m}^{-2}\) 2. \(0.25\times10^{-3}~\text{C m}^{-2}\)
3. \(4\times10^{-3}~\text{C m}^{-2}\) 4. \(0.4\times10^{-3}~\text{C m}^{-2}\)
Subtopic:  Electric Charge |
 53%
Level 3: 35%-60%
NEET - 2024
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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, \(k=\dfrac{1}{4\pi\varepsilon_0}\) 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 \(=9.11\times 10^{-31}~\text{kg},\) the mass of the proton \(=1.67\times 10^{-27}~\text{kg}\) )
1. \(10^{20}\) 2. \(10^{30}\)
3. \(10^{40}\) 4. \(10\)
Subtopic:  Coulomb's Law |
 62%
Level 2: 60%+
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:
\(\left(\dfrac{1}{4 \pi \varepsilon_0}=9 \times 10^9~ \text{Nm}^2 \text{C}^{-2}\right)\)
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 |
 76%
Level 2: 60%+
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 |
 79%
Level 2: 60%+
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 the mass of hydrogen \(m_h = 1.67\times 10^{-27}~\text{kg}\))
1. \(10^{-23}~\text{C}\)
2. \(10^{-37}~\text{C}\)
3. \(10^{-47}~\text{C}\)
4. \(10^{-20}~\text{C}\)

Subtopic:  Coulomb's Law |
 66%
Level 2: 60%+
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 |
 77%
Level 2: 60%+
NEET - 2016
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A charge \(q\) is placed at the centre of the line joining two equal positive charges \(Q.\) The system of the three charges will be in equilibrium, if \(q\) is equal to:
1. \(\dfrac{-Q}{4}\) 2. \(\dfrac{Q}{4}\)
3. \(\dfrac{-Q}{2}\) 4. \(\dfrac{Q}{2}\)
Subtopic:  Coulomb's Law |
 66%
Level 2: 60%+
NEET - 2013
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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. \(\dfrac{r}{\sqrt[3]{2}}\) 2. \(\dfrac{r}{\sqrt[2]{2}}\)
3. \(\dfrac{2r}{3}\) 4. none of the above
Subtopic:  Coulomb's Law |
 71%
Level 2: 60%+
AIPMT - 2013
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Two identical rectangular plane sheet \(A\) and \(B\) each of surface charge density \(\varepsilon_0~ \text{Cm}^{-2}\) are placed parallel to each other as shown in figure. The electric field at the mid point \(P\) will be:
1. \(2 ~\text{NC}^{-1}\) 2. \(1~\text{NC}^{-1}\)
3. \(0.5~\text{NC}^{-1}\) 4. zero
Subtopic:  Electric Field |
 79%
Level 2: 60%+
NEET - 2024
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A particle of mass \(m\) and charge \(q\) is placed in a uniform electric field \(E\) at \(t=0~\text s.\) The kinetic energy of the particle after time \(t\) is:
1. \(\dfrac{Eqm}{t}\) 2. \(\dfrac{E^2q^2t^2}{2m}\)
3. \(\dfrac{2E^2t^2}{qm}\) 4. \(\dfrac{Eq^2m}{2t^2}\)
Subtopic:  Electric Field |
 83%
Level 1: 80%+
NEET - 2024
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