1
JEE Main 2020 (Online) 2nd September Evening Slot
+4
-1
A small point mass carrying some positive charge on it, is released from the edge of a table. There is a uniform electric field in this region in the horizontal direction. Which of the following options then correctly describe the trajectory of the mass?
(Curves are drawn schematically and are not to scale).
A
B
C
D
2
JEE Main 2020 (Online) 2nd September Evening Slot
+4
-1
A charge Q is distributed over two concentric conducting thin spherical shells radii r and R (R > r). If the surface charge densities on the two shells are equal, the electric potential at the common centre is :
A
$${1 \over {4\pi {\varepsilon _0}}}{{\left( {R + r} \right)} \over {\left( {{R^2} + {r^2}} \right)}}$$Q
B
$${1 \over {4\pi {\varepsilon _0}}}{{\left( {R + r} \right)} \over {2\left( {{R^2} + {r^2}} \right)}}Q$$
C
$${1 \over {4\pi {\varepsilon _0}}}{{\left( {R + 2r} \right)Q} \over {2\left( {{R^2} + {r^2}} \right)}}$$
D
$${1 \over {4\pi {\varepsilon _0}}}{{\left( {2R + r} \right)} \over {\left( {{R^2} + {r^2}} \right)}}Q$$
3
JEE Main 2020 (Online) 2nd September Morning Slot
+4
-1
A charged particle (mass m and charge q)
moves along X-axis with velocity V0. When it
passes through the origin it enters a region having uniform electric field
$$\overrightarrow E = - E\widehat j$$ which extends upto x = d.
Equation of path of electron in the region x > d is
A
y = $${{qEd} \over {mV_0^2}}\left( {x - d} \right)$$
B
y = $${{qEd} \over {mV_0^2}}\left( {{d \over 2} - x} \right)$$
C
y = $${{qEd} \over {mV_0^2}}x$$
D
y = $${{qE{d^2}} \over {mV_0^2}}x$$
4
JEE Main 2020 (Online) 9th January Morning Slot
+4
-1
Consider a sphere of radius R which carries a uniform charge density $$\rho$$. If a sphere of radius $${{R \over 2}}$$ is carved out of it, as shown, the ratio $${{\left| {\overrightarrow {{E_A}} } \right|} \over {\left| {\overrightarrow {{E_B}} } \right|}}$$ of magnitude of electric field $${\overrightarrow {{E_A}} }$$ and $${\overrightarrow {{E_B}} }$$, respectively, at points A and B due to the remaining portion is :
A
$${{17} \over {54}}$$
B
$${{18} \over {54}}$$
C
$${{18} \over {34}}$$
D
$${{21} \over {34}}$$
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