1
JEE Main 2020 (Online) 5th September Morning Slot
+4
-1
A square loop of side 2$$a$$, and carrying current I, is kept in XZ plane with its centre at origin. A long wire carrying the same current I is placed parallel to the z-axis and passing through the point (0, b, 0), (b >> a). The magnitude of the torque on the loop about zaxis is given by :
A
$${{2{\mu _0}{I^2}{a^2}} \over {\pi b}}$$
B
$${{{\mu _0}{I^2}{a^2}} \over {2\pi b}}$$
C
$${{{\mu _0}{I^2}{a^3}} \over {2\pi {b^2}}}$$
D
$${{2{\mu _0}{I^2}{a^3}} \over {\pi {b^2}}}$$
2
JEE Main 2020 (Online) 4th September Evening Slot
+4
-1
A circular coil has moment of inertia 0.8 kg m2 around any diameter and is carrying current to produce a magnetic moment of 20 Am2 . The coil is kept initially in a vertical position and it can rotate freely around a horizontal diameter. When a uniform magnetic field of 4 T is applied along the vertical,it starts rotating around its horizontal diameter. The angular speed the coil acquires after rotating by 60o will be:
A
10 $$\pi$$ rad s–1
B
20 $$\pi$$ rad s–1
C
$$10{\left( 3 \right)^{1/4}}$$ rad s–1
D
3
JEE Main 2020 (Online) 4th September Morning Slot
+4
-1
A wire A, bent in the shape of an arc of a circle, carrying a current of 2 A and having radius 2 cm and another wire B, also bent in the shape of arc of a circle, carrying a current of 3 A and having radius of 4 cm, are placed as shown in the figure. The ratio of the magnetic fields due to the wires A and B at the common centre O is :
A
4 : 6
B
6 : 4
C
2 : 5
D
6 : 5
4
JEE Main 2020 (Online) 3rd September Morning Slot
+4
-1
A charged particle carrying charge 1 $$\mu$$C is moving
with velocity $$\left( {2\widehat i + 3\widehat j + 4\widehat k} \right)$$ ms–1. If an external
magnetic field of $$\left( {5\widehat i + 3\widehat j - 6\widehat k} \right)$$× 10–3 T exists in the region where the particle is moving then the
force on the particle is $$\overrightarrow F$$ × 10–9 N. The vector $$\overrightarrow F$$ is :
A
$${ - 0.30\widehat i + 0.32\widehat j - 0.09\widehat k}$$
B
$${ - 300\widehat i + 320\widehat j - 90\widehat k}$$
C
$${ - 30\widehat i + 32\widehat j - 9\widehat k}$$
D
$${ - 3.0\widehat i + 3.2\widehat j - 0.9\widehat k}$$
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