1
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
A galvanometer with its coil resistance 25 $$\Omega$$ requires a current of 1 mA for its full deflection. In order to construct an ammeter to read upto a current of 2 A, the approximate value of the shunt resistance should be :
A
$$2.5 \times {10^{ - 3}}\,\Omega$$
B
$$1.25 \times {10^{ - 2}}\Omega$$
C
$$1.25 \times {10^{ - 3}}\Omega$$
D
$$2.5 \times {10^{ - 2}}\Omega$$
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
A charge q is spread uniformly over an insulated loop of radius r. If it is rotated with an angular velocity $$\omega$$ with resect to normal axis then the magnetic moment of the loop is :
A
q $$\omega$$r2
B
$${4 \over 3}$$ q $$\omega$$r2
C
$${3 \over 2}$$ q $$\omega$$r2
D
$${1 \over 2}$$ q $$\omega$$r2
3
JEE Main 2018 (Offline)
+4
-1
An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii re, rp, r$$_\alpha$$ respectively in a uniform magnetic field B. The relation between re, rp, r$$_\alpha$$ is:
A
re < r$$_\alpha$$ < rp
B
re > rp = r$$_\alpha$$
C
re < rp = r$$_\alpha$$
D
re < rp < r$$_\alpha$$
4
JEE Main 2018 (Offline)
+4
-1
The dipole moment of a circular loop carrying a current I, is m and the magnetic field at the centre of the loop is B1. When the dipole moment is doubled by keeping the current constant, the magnetic field at the centre of the loop is $${{B_2}}$$. The ratio $${{{B_1}} \over {{B_2}}}$$ is:
A
2
B
$$\sqrt 3$$
C
$$\sqrt 2$$
D
$$1 \over \sqrt 2$$
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