1
WB JEE 2022
MCQ (Single Correct Answer)
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WB JEE 2022 Physics - Electrostatics Question 14 English

A neutral conducting solid sphere of radius R has two spherical cavities of radius a and b as shown in the figure. Centre to centre distance between two cavities is c. qa and qb charges are placed at the centres of cavities respectively. The force between qa and qb is

A
$${1 \over {4\pi {\varepsilon _0}}}{{{q_a}{q_b}} \over {{c^2}}}$$
B
$${1 \over {4\pi {\varepsilon _0}}}{q_a}{q_b}\left( {{1 \over {{a^2}}} + {1 \over {{b^2}}}} \right)$$
C
zero
D
insufficient data
2
WB JEE 2022
MCQ (Single Correct Answer)
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Consider two concentric conducting sphere of radii R and 2R respectively. The inner sphere is given a charge +Q. The other sphere is grounded. The potential at $$r = {{3R} \over 2}$$ is

A
$${1 \over {4\pi {\varepsilon _0}}}{Q \over {6R}}$$
B
0
C
$${1 \over {4\pi {\varepsilon _0}}}{{2Q} \over {3R}}$$
D
$${1 \over {4\pi {\varepsilon _0}}}{Q \over R}$$
3
WB JEE 2021
MCQ (Single Correct Answer)
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WB JEE 2021 Physics - Electrostatics Question 16 English
The variation of electric field along the Z-axis due to a uniformly charged circular ring of radius a in XY-plane as shown in the figure. The value of coordinate M will be
A
$${1 \over 2}$$
B
$$\sqrt 2 $$
C
1
D
$${1 \over {\sqrt 2 }}$$
4
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
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A metal sphere of radius R carrying charge q is surrounded by a thick concentric metal shell of inner and outer radii a and b, respectively. The net charge on the shell is zero. The potential at the centre of the sphere, when the outer surface of the shell is grounded will be
A
$${q \over {4\pi {\varepsilon _0}}}\left( {{1 \over a} - {1 \over b}} \right)$$
B
$${q \over {4\pi {\varepsilon _0}}} - {1 \over a}$$
C
$${q \over {4\pi {\varepsilon _0}}}\left( {{1 \over R} - {1 \over a}} \right)$$
D
$${q \over {4\pi {\varepsilon _0}}} - {1 \over R}$$
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