HARD
JEE Main
IMPORTANT
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The potential (in volts) of a charge distribution is given by

Vz=30-5z2 for z1 m

Vz=35-10 z for z1 m .

Vz does not depend on x and y. If this potential is generated by a constant charge per unit volume ρ0 (in units of ϵ0 ) which is spread over a certain region, then choose the correct statement.

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Important Questions on Electrostatics

HARD
JEE Main
IMPORTANT
The region between two concentric spheres of radii 'a' and 'b', respectively (see figure), has volume charge density ρ=Ar , where A is a constant and r is the distance from the centre. At the centre of the spheres is a point charge Q. The value of A such that the electric field in the region between the spheres will be constant, is:

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HARD
JEE Main
IMPORTANT
A combination of capacitors is set up as shown in the figure. The magnitude of the electric field, due to a point charge Q (having a charge equal to the sum of the charges on the 4 μF and 9 μF capacitors), at a point distant 30 m from it, would equal:
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HARD
JEE Main
IMPORTANT
Within a spherical charge distribution of charge density ρr,  N equipotential surfaces of potential V0, V0+V, V0+2V,V0+NV V>0, are drawn and have increasing radii r0, r1, r2,rN, respectively. If the difference in the radii of the surfaces is constant for all values of V0 and V then :
MEDIUM
JEE Main
IMPORTANT

Figure shows a network of capacitors where the number indicates capacitances in micro Farad. The value of capacitance C if the equivalent capacitance between point A and B is to be 1 μF is :

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EASY
JEE Main
IMPORTANT
Shown in the figure are two point charges +Q and -Q inside the cavity of a spherical shell. The charges are kept near the surface of the cavity on opposite sides of the centre of the shell. If σ1 is the surface charge on the inner surface and Q1 net charge on it and σ2 the surface charge on the outer surface and Q2 net charge on it then:

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HARD
JEE Main
IMPORTANT

A thin disc of radius b=2a has a concentric hole of radius a in it (see figure). It carries uniform surface charge σ  on it. If the electric field on its axis at a height hh<<a from its centre is given as Ch then the value of C is

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MEDIUM
JEE Main
IMPORTANT
In the given circuits a and b, switches S1 and S2 are closed at t=0 and kept close for a long time. The variation of currents in the two circuits for t0 are shown in the options. (Figures are schematic and not drawn to scale.)
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MEDIUM
JEE Main
IMPORTANT
If the capacitance of a nanocapacitor is measured in terms of a unit u,  made by combining the electronic charge e, Bohr radius a0, Planck's constant h and speed of light c then