1
JEE Main 2019 (Online) 10th January Morning Slot
+4
-1
An insulating thin rod of length $$l$$ has a linear charge density $$\rho \left( x \right)$$ = $${\rho _0}{x \over l}$$ on it. The rod is rotated about an axis passing through the origin (x = 0) and perpendicular to the rod. If the rod makes n rotations per second, then the time averaged magnetic moment of the rod is -
A
$${\pi \over 3}n\rho {l^3}$$
B
$${\pi \over 4}n\rho {l^3}$$
C
$$n\rho {l^3}$$
D
$$\pi n\rho {l^3}$$
2
JEE Main 2019 (Online) 9th January Evening Slot
+4
-1
A particle having the same charge as of electron moves in a ciurcular path of radius 0.5 cm under the influence of a magnetic field 0f 0.5 T. If an electric field of 100 V/m makes it to move in a straight path, then the mass of the particle is (Given charge of electron = 1.6 $$\times$$ 10$$-$$19C)
A
9.1 $$\times$$ 10$$-$$31 kg
B
1.6 $$\times$$ 10$$-$$27 kg
C
1.6 $$\times$$ 10$$-$$19 kg
D
2.0 $$\times$$ 10$$-$$24 kg
3
JEE Main 2019 (Online) 9th January Evening Slot
+4
-1
One of the two identical conducting wires of length L is bent in the form of a circular loop and the other one into a circular coil of N identical turns. If the same current is passed in both, the radio of the magnetic field at the central of the loop (BL) to that at the center of the coil (BC), i.e. $${{{B_L}} \over {{B_C}}}$$ will be :
A
N
B
$${1 \over N}$$
C
N2
D
$${1 \over {{N^2}}}$$
4
JEE Main 2019 (Online) 9th January Morning Slot
+4
-1
A current loop, having two circular arcs joined by two radial lines is shown in the figure. It carries a current of 10 A. The magnetic field at point O will be close to :

A
1.0 $$\times$$ 10$$-$$7 T
B
1.5 $$\times$$ 10$$-$$7 T
C
1.5 $$\times$$ 10$$-$$5 T
D
1.0 $$\times$$ 10$$-$$5 T
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