1
JEE Main 2022 (Online) 25th July Evening Shift
+4
-1 An electron with energy 0.1 keV moves at right angle to the earth's magnetic field of 1 $$\times$$ 10$$-$$4 Wbm$$-$$2. The frequency of revolution of the electron will be

(Take mass of electron = 9.0 $$\times$$ 10$$-$$31 kg)

A
$$1.6 \times 10^{5} \mathrm{~Hz}$$
B
$$5.6 \times 10^{5} \mathrm{~Hz}$$
C
$$2.8 \times 10^{6} \mathrm{~Hz}$$
D
$$1.8 \times 10^{6} \mathrm{~Hz}$$
2
JEE Main 2022 (Online) 25th July Morning Shift
+4
-1 Two charged particles, having same kinetic energy, are allowed to pass through a uniform magnetic field perpendicular to the direction of motion. If the ratio of radii of their circular paths is $$6: 5$$ and their respective masses ratio is $$9: 4$$. Then, the ratio of their charges will be :

A
8 : 5
B
5 : 4
C
5 : 3
D
8 : 7
3
JEE Main 2022 (Online) 25th July Morning Shift
+4
-1 The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by :

A
$$\vec{\mu}_{\mathrm{L}}=\frac{\overrightarrow{\mathrm{eL}}}{2 \mathrm{~m}}$$
B
$$\vec{\mu}_{\mathrm{L}}=-\frac{\overrightarrow{\mathrm{eL}}}{2 \mathrm{~m}}$$
C
$$\vec{\mu}_{l}=-\frac{\overrightarrow{e L}}{\mathrm{~m}}$$
D
$$\vec{\mu}_{l}=\frac{2 \overrightarrow{\mathrm{eL}}}{\mathrm{m}}$$
4
JEE Main 2022 (Online) 30th June Morning Shift
+4
-1

A coil of n number of turns wound tightly in the form of a spiral with inner and outer radii r1 and r2 respectively. When a current of strength I is passed through the coil, the magnetic field at its centre will be :

A
$${{{\mu _0}nI} \over {2({r_2} - {r_1})}}$$
B
$${{{\mu _0}nI} \over {{r_2}}}$$
C
$${{{\mu _0}nI} \over {{r_2} - {r_1}}}{\log _e}{{{r_1}} \over {{r_2}}}$$
D
$${{{\mu _0}nI} \over {2({r_2} - {r_1})}}{\log _e}{{{r_2}} \over {{r_1}}}$$
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