Suppose the charge of a proton and an electron differ slightly. One of them is \(\text- e\) and 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: [Given the mass of hydrogen, \(m_h = 1.67\times 10^{-27}~\text{kg}\)]
1. \(10^{-20}~\text{C}\)
2. \(10^{-23}~\text{C}\)
3. \(10^{-37}~\text{C}\)
4. \(10^{-47}~\text{C}\)

Subtopic:  Coulomb's Law |
 64%
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(d < < l) 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:

(a) \(v \propto x\)

(b) \(v \propto x^{\frac{-1}{2}}\)

(c) \(v \propto x^{-1}\)

(d) \(v \propto x^{\frac{1}{2}}\)
 

Subtopic:  Coulomb's Law |
 68%
From NCERT
NEET - 2016
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The electric field in a certain region is acting radially outward and is given by E=Ar. A charge contained in a sphere of radius 'a' centered at the origin of the field will be given by

1. 4πoAa2

2. πoAa2

3. 4πoAa3

4. oAa2

Subtopic:  Gauss's Law |
 70%
From NCERT
NEET - 2015
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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. Now the strings are rigidly clamped at half the height. The equilibrium separation between the balls now become:

1. (1/√2)2

2. (r/23) 

3. (2r/√3)

4. (2r/3)

Subtopic:  Coulomb's Law |
 76%
From NCERT
NEET - 2013
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What is the flux through a cube of side 'a' if a point charge q is at one of its corners?

1. 2qε0                                         

2. q8ε0

3. qε0                                         

4. q2ε06a2

Subtopic:  Gauss's Law |
 86%
From NCERT
NEET - 2012
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A charge Q is enclosed by a Gaussian spherical surface of radius R. If the radius is doubled, then the outward electric flux will

1. be reduced to half                                 

2. remain the same

3. be doubled

4. increase four times

Subtopic:  Gauss's Law |
 84%
From NCERT
NEET - 2011
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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 being the charge on an electron)

1. 4πεFd2 e2                  2. 4πεFe2d2

3. 4πεFd2e2               4. 4πεFd2q2

 

Subtopic:  Coulomb's Law |
 76%
From NCERT
NEET - 2010
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A surface of side L metre in the plane of the paper is placed in a uniform electric field E(volt/m) acting along the same plane at an angle θ with the horizontal side of the square as shown in figure. The electric flux linked to the surface in unit of V-m, is

(1) EL2 

(2) EL2cosθ

(3) EL2sinθ

(4) 0

Subtopic:  Gauss's Law |
 70%
From NCERT
NEET - 2010
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Two parallel metal plates having charges +Q and -Q faces each other at a certain distance between them. If the plates are now dipped in kerosene oil tank, the electric field between the plates will

(1) become zero                                   

(2) increase

(3) decrease                                         

(4) remain same

Subtopic:  Electric Field |
 70%
From NCERT
NEET - 2010
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The electric field at a distance 3R2 from the centre of a charged conducting spherical shell of radius R is E. The electric field at a distance R2 from the centre of the sphere is 

1. zero                                     2. E

3. E2                                       4. E3

Subtopic:  Electric Field |
 81%
From NCERT
NEET - 2010
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