1
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Three infinite plane sheets carrying uniform charge densities $$-$$ $$\sigma$$, 2$$\sigma$$, 4$$\sigma$$ are placed parallel to XZ-plane at Y = a, 3a, 4a respectively. The electric field at the point (0, 2a, 0) is
A
$${{5\sigma } \over {2{\varepsilon _0}}}\widehat j$$
B
$$ - {{7\sigma } \over {2{\varepsilon _0}}}\widehat j$$
C
$${\sigma \over {2{\varepsilon _0}}}\widehat j$$
D
$${{5\sigma } \over { - 2{\varepsilon _0}}}\widehat j$$
2
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Two point charges +q1 and +q2 are placed a finite distance d apart. It is desired to put a third charge q3 in between these two charges, so that q3 is in equilibrium. This is
A
possible only if q3 is negative.
B
possible only if q3 is positive.
C
possible irrespective of the sign of q3.
D
not possible at all.
3
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
Change Language
WB JEE 2021 Physics - Magnetism Question 12 English
Consider two infinitely long wires parallel to Z-axis carrying same current I in the positive z-direction. One wire passes through the point L at coordinates ($$-$$1, +1) and the other wire passes through the point M at coordinates ($$-$$1, $$-$$1). The resultant magnetic field at the origin O will be
A
$${{{\mu _0}I} \over {2\sqrt 2 \pi }}\widehat j$$
B
$${{{\mu _0}I} \over {2\pi }}\widehat j$$
C
$${{{\mu _0}I} \over {2\sqrt 2 \pi }}\widehat i$$
D
$${{{\mu _0}I} \over {4\pi }}\widehat i$$
4
WB JEE 2021
MCQ (Single Correct Answer)
+1
-0.25
Change Language
A thin charged rod is bent into the shape of a small circle of radius R, the charge per unit length of the rod being $$\lambda$$. The circle is rotated about its axis with a time period T and it is found the magnetic field at a distance d away (d >> R) from the centre and on the axis, varies as $$R^m \over d^n$$. The values of m and n respectively are
A
m = 2, n = 2
B
m = 2, n = 3
C
m = 3, n = 2
D
m = 3, n = 3
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