NEET Free Online Mock Test - 2019

NEET Physics  Electrostatics  Practice Q & A

1. Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of 30° with each other. When suspended in a liquid of density 0.8 g cm–3, the angle remains the same. If density of the material of the sphere is 1.6 g cm–3, the dielectric constant of the liquid is

1 4 3 2

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2. Two charges, each equal to q, are kept at x = – a and x = a on the x–axis. A particle of mass m and charge q0 = q/2 is placed at the origin. If charge q0 is given a small displacement (y << a) along the y–axis, the net force acting on the particle is proportional to

y –y $\dfrac{1}{y}$ –$\dfrac{1}{y}$

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3. An electric dipole is placed at an angle of 30° with an electric field intensity 2 × 105 N/C. It experiences a torque equal to 4 N m. The charge on the dipole, if the dipole length is 2 cm, is

8 mC 2 mC 5 mC 7 μC

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4. Three concentric metallic spherical shells of radii R, 2R, 3R, are given charges Q1, Q2, Q3, respectively. It is found that the surface charge densities on the outer surfaces of the shells are equal. Then, the ratio of the charges given to the shells, Q1 : Q2 : Q3, is

1 : 2 : 3 1 : 3 : 5 1 : 4 : 9 1 : 8 : 18

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5. A parallel plate air capacitor of capacitance C is connected to a cell of emf V and then disconnected from it. A dielectric slab of dielectric constant K, which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?

The potential difference between the plates decreases K times The energy stored in the capacitor decreases K times The change in energy stored is $\dfrac{1}{2}CV^2\left(\dfrac{1}{K} – 1\right)$ The charge on the capacitor is not conserved

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6. Two spherical conductors A and B of radii 1 mm and 2 mm are separated by a distance of 5 cm and are uniformly charged. If the spheres are connected by a conducting wire then in equilibrium condition, the ratio of the magnitude of the electric fields at the surface of spheres A and B is

1 : 4 4 : 1 1 : 2 2 : 1

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7. A, B and C are three points in a uniform electric field. The electric potential is
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Maximum at A Maximum at B Maximum at C Same at all the three points A, B and C

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8. 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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360 N/C 420 N/C 480 N/C 240 N/C

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9. Consider a neutral conducting sphere. A positive point charge is placed outside the sphere. The net charge on the sphere is then,

negative and distributed uniformly over the surface of the sphere negative and appears only at the point on the sphere closest to the point charge negative and distributed non–uniformly over the entire surface of the sphere zero

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10. A capacitor of 2 μF is charged as shown in the diagram. When the switch S is turned to position 2, the percentage of its stored energy dissipated is
capacitor1.PNG" />

75% 80% 0% 20%

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