1
NEET 2025
MCQ (Single Correct Answer)
+4
-1
Change Language

A model for quantized motion of an electron in a uniform magnetic field $B$ states that the flux passing through the orbit of the electron in $n(h l e)$ where $n$ is an integer, $h$ is Planck's constant and $e$ is the magnitude of electron's charge. According to the model, the magnetic moment of an electron in its lowest energy state will be ( $m$ is the mass of the electron)

A
$\frac{h e B}{\pi m}$
B
$\frac{h e B}{2 \pi m}$
C
$\frac{h e}{\pi m}$
D
$\frac{h e}{2 \pi m}$
2
NEET 2025
MCQ (Single Correct Answer)
+4
-1
Change Language

An electron (mass $9 \times 10^{-31} \mathrm{~kg}$ and charge $1.6 \times 10^{-19} \mathrm{C}$ ) moving with speed $c / 100(c=$ speed of light) is injected into a magnetic field $\vec{B}$ of magnitude $9 \times 10^{-4} \mathrm{~T}$ perpendicular to its direction of motion. We wish to apply an uniform electric field $\vec{E}$ together with the magnetic field so that the electron does not deflect from its path. Then (speed of light $c=3$ $\times 10^3 \mathrm{~ms}^{-1}$)

A
$\vec{E}$ is parallel to $\vec{B}$ and its magnitude is $27 \times 10^2 \mathrm{~V} \mathrm{~m}^{-1}$
B
$\vec{E}$ is parallel to $\vec{B}$ and its magnitude is $27 \times 10^4 \mathrm{~V} \mathrm{~m}^{-1}$
C
$\vec{E}$ is perpendicular to $\vec{B}$ and its magnitude is $27 \times 10^4 \mathrm{~V} \mathrm{~m}^{-1}$
D
$\vec{E}$ is perpendicular to $\vec{B}$ and its magnitude is $27 \times 10^2 \mathrm{~V} \mathrm{~m}^{-1}$
3
NEET 2025
MCQ (Single Correct Answer)
+4
-1
Change Language

A 2 amp current is flowing through two different small circular copper coils having radii ratio $1: 2$. The ratio of their respective magnetic moments will be

A
$2: 1$
B
$4: 1$
C
$1: 4$
D
$1: 2$
4
NEET 2024
MCQ (Single Correct Answer)
+4
-1
Change Language

A tightly wound 100 turns coil of radius $$10 \mathrm{~cm}$$ carries a current of $$7 \mathrm{~A}$$. The magnitude of the magnetic field at the centre of the coil is (Take permeability of free space as $$4 \pi \times 10^{-7} \mathrm{SI}$$ units):

A
44 mT
B
4.4 T
C
4.4 mT
D
44 T
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