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Two metallic spheres of same mass are given equal and opposite charges. Then,

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Important Questions on Electrostatics

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Two charges of equal magnitudes and at a distance r exert a force F on each other. If the charges are halved and distance between them is doubled, then the new force acting on each charge is

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The charge present in a doubly ionized helium atom is
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Suppose the charge of a proton and an electron differ slightly. One of them is e, the other is e+Δe. If the net electrostatic force and gravitational force between two hydrogen atoms placed at a distance d (much greater than atomic size) apart is zero, then Δe is of the order of [Given mass of hydrogen mh= 1.67×1027 kg]
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Two electrons are moving with equal speed of 5×105 m s-1 parallel to each other. The ratio of the electrostatic to the magnetic force between them is
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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 Å apart is,
me9×10-31 kg, e=1.6×10-19 C (Take 14πε0=9×109 N m2 C-2)
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The dimensional formula of coefficient of permittivity for free space (ε0) in the equation F=14πε0q1q2r2, where symbols have their usual meanings, is
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Two equally charged metal spheres A and B repel each other with a force of 4×10-5 N. Another identical uncharged sphere C is touched to A and then placed at the mid point of the line joining the spheres A and B. The net electric force on the sphere C is
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The attractive force results when a glass rod rubbed with a silk and a plastic rod rubbed with a fur brings together. During friction which type of charges are developed on glass rod and plastic rod? 
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If two electrons are forced to come closer to each other, the potential energy of the system of 2 electrons will
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Two small metal spheres A and B charged positively are separated by 2 m in air. The force on a charge of +1 C placed on the line joining the centres of the spheres and at a distance of 0.5 m from A is found to be zero. The ratio qA:qB of charges on A and B is
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When a number of charged liquid drops coalesce, which of the following quantity does not change?
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Three Point charges each equal to +q are placed at the vertices of an equilateral triangle of side 'l'. The net force on a charge q1 placed at the centre of the triangle is
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Two point charges A and B, having charges +Q and -Q respectively, are placed at certain distance apart and force acting between them is F. If  25% charge of A is transferred to B, then the force between the charges becomes
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Four point charges qA=2 μC, qB=-5 μC, qC=2 μC, qD=-5 μC are located at the corners of a square ABCD of side 10 cm. The force acting on a charge of 1 μC placed at centre of the square is

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Two identical conducting spheres A and B carry equal charge. They are initially separated by a distance much larger than their diameters and the force between them is F. A third identical conducting sphere C is uncharged. Sphere C is first touched to A, then to C and removed. As a result, the force between A and B now is
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Four charges each equal to (-Q) are placed at the four corners of a square and a charge q is placed at its centre. If the system of charges is in equilibrium, the value of q is
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If a body gives out 109 electrons every second, how much time is required to get a total charge of 1 C from it ?
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As shown in the figure, two particles, each of mass 'm' tied at the ends of a light string of length 2a are kept on a frictionless horizontal surface. When the mid point (P) of the string is pulled vertically upwards with a small but constant force F, the particles move towards each other on the surface. Magnitude of acceleration of each particle, when the separation between them becomes 2x is

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The number of electrons in one coulomb charge is