A tightly wound \(100\) turns coil of radius \(10~\text{cm}\) carries a current of \(7~\text A\). The magnitude of the magnetic field at the centre of the coil is: (Take permeability of free space as \(​4 \pi \times 10^{-7​}\)SI units):
1. \(4.4~\text T\)
2. \(4.4~\text {mT}\)
3. \(44~\text T\)
4. \(44~\text {mT}\)

Subtopic:  Magnetic Field due to various cases |
 71%
From NCERT
NEET - 2024
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A model for the quantized motion of an electron in a uniform magnetic field \(B\) states that the flux passing through the orbit of the electron is \(n(h/e)\) where \(n\) is an integer, \(h\) is Planck's constant and \(e\) is the magnitude of the electron's charge. According to the model, the magnetic moment of an electron is its lowest energy state will be (\(m\) is the mass of the electron):
1. \(\dfrac{heB}{\pi m}\) 2. \(\dfrac{heB}{2\pi m}\)
3. \(\dfrac{he}{\pi m}\) 4. \(\dfrac{he}{2\pi m}\)
Subtopic:  Magnetic Moment |
From NCERT
NEET - 2025
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An electron (mass \(9\times10^{-31}~\text{kg}\) and charge \(1.6\times10^{-19}~\text C\)) moving with speed \(c/100\) (\(c\)=speed of light) is injected into a magnetic field \(\vec B\) of magnitude \(9\times10^{-4}~\text{T}\) 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 \(c=3\times10^8~\text{ms}^{-1}\))
1. \(\vec E\) is parallel to \(\vec B\) and its magnitude is \(27\times10^{2}~\text{V m}^{-1}\)
2. \(\vec E\) is parallel to \(\vec B\) and its magnitude is \(27\times10^{4}~\text{V m}^{-1}\)
3. \(\vec E\) is perpendicular to \(\vec B\) and its magnitude is \(27\times10^{4}~\text{V m}^{-1}\)
4. \(\vec E\) is perpendicular to \(\vec B\) and its magnitude is \(27\times10^{2}~\text{V m}^{-1}\)
Subtopic:  Lorentz Force |
From NCERT
NEET - 2025
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A \(2~\text{amp}\) current is flowing through two different small circular copper coils having radii ratio \(1:2.\) The ratio of their respective magnetic moments will be:
1. \(2: 1\)
2. \(4: 1\)
3. \(1: 4\)
4. \(1: 2\)
Subtopic:  Magnetic Moment |
 64%
From NCERT
NEET - 2025
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A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:
1. will turn towards right of direction of motion
2. will turn towards left of direction of motion
3. speed will decrease
4. speed will increase
Subtopic:  Lorentz Force |
 65%
From NCERT
NEET - 2023
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A long straight wire of length \(2\) m and mass \(250\) g is suspended horizontally in a uniform horizontal magnetic field of \(0.7\) T. The amount of current flowing through the wire will be:
(\(g=9.8~\text{ms}^{-2}\))
1. \(2.45\) A
2. \(2.25\) A
3. \(2.75\) A
4. \(1.75\) A
Subtopic:  Lorentz Force |
 78%
From NCERT
NEET - 2023
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A very long conducting wire is bent in a semi-circular shape from \(A\) to \(B\) as shown in the figure. The magnetic field at the point \(P\) for steady current configuration is given by:
      
1. \(\dfrac{\mu_0 i}{4 R}\left[1-\dfrac{2}{\pi}\right]\) pointed into the page
2. \(\dfrac{\mu_0 i}{4 R}\) pointed into the page
3. \(\dfrac{\mu_0 i}{4 R}\) pointed away from the page
4. \(\dfrac{\mu_0 i}{4 R}\left[1-\dfrac{2}{\pi}\right]\) pointed away from the page
Subtopic:  Magnetic Field due to various cases |
 57%
From NCERT
NEET - 2023
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A wire carrying a current \(I\) along the positive \(x\)-axis has length \(L\). It is kept in a magnetic field \(\overrightarrow{B}=(2 \hat{i}+3 \hat{j}-4 \hat{k})~\text{T}\). The magnitude of the magnetic force acting on the wire is:
1. \(\sqrt{3}IL\)
2. \(3IL\)
3. \(\sqrt{5}IL\)
4. \(5IL\)
Subtopic:  Lorentz Force |
 64%
From NCERT
NEET - 2023
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The magnetic field on the axis of a circular loop of radius \(100~\text{cm}\) carrying current \(I=\sqrt{2}~\text{A},\) at a point \(1~\text{m}\) away from the centre of the loop is given by:
1. \(3.14 \times 10^{-7} ~\text{T} \)
2. \(6.28 \times 10^{-7} ~\text{T} \)
3. \(3.14 \times 10^{-4} ~\text{T} \)
4. \(6.28 \times 10^{-4} ~\text{T}\)
Subtopic:  Magnetic Field due to various cases |
 58%
From NCERT
NEET - 2022
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Two very long, straight, parallel conductor \(\mathrm{A}\) and \(\mathrm{B}\) carry current of \(5~\text{A}\)  and \(10~\text{A}\) respectively and are at a distance of \(10~\mathrm{cm}\) from each other. The direction of the current in the two conductors is the same. The force acting per unit length between two conductors is:
(\(\mu_0=4\pi \times 10^{-7}\) SI unit)
1. \(2\times10^{-4}~\text{Nm}^{-1}\)  and is attractive
2. \(2\times10^{-4}~\text{Nm}^{-1}\)  and is repulsive
3. \(1\times10^{-4}~\text{Nm}^{-1}\) and is attractive
4. \(1\times10^{-4}~\text{Nm}^{-1}\)  and is repulsive
Subtopic:  Force between Current Carrying Wires |
 75%
From NCERT
NEET - 2022
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