Q. No.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 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. \(5IL\)
1. \(\sqrt{3}IL\)
2. \(3IL\)
3. \(\sqrt{5}IL\)
4. \(5IL\)
Subtopic: Lorentz Force |
64%
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
(\(g=9.8~\text{ms}^{-2}\))
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 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 strong magnetic field is applied along the direction of the velocity of an electron. The electron would move along:
| 1. | a parabolic path |
| 2. | the original path |
| 3. | a helical path |
| 4. | a circular path |
Subtopic: Lorentz Force |
67%
From NCERT
NEET - 2022
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An infinitely long straight conductor carries a current of \(5~\text{A}\) as shown. An electron is moving with a speed of \(10^5~\text{m/s}\) parallel to the conductor. The perpendicular distance between the electron and the conductor is \(20~\text{cm}\) at an instant. Calculate the magnitude of the force experienced by the electron at that instant.
1. \(4\pi\times 10^{-20}~\text{N}\)
2. \(8\times 10^{-20}~\text{N}\)
3. \(4\times 10^{-20}~\text{N}\)
4. \(8\pi\times 10^{-20}~\text{N}\)
Subtopic: Lorentz Force |
67%
From NCERT
NEET - 2021
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In the product
\(\vec{F}=q\left ( \vec{v}\times \vec{B} \right )\)
\(~~~=q\vec{v}\times \left ( B\hat{i}+B\hat{j}+B_0\hat{k} \right )\)
For \(q=1\) and \(\vec{v}=2\hat{i}+4\hat{j}+6\hat{k}\)
and \(\vec{F}=4\hat{i}-20\hat{j}+12\hat{k}\)
What will be the complete expression for \(\vec{B}\)?
1. \(8\hat{i}+8\hat{j}-6\hat{k}\)
2. \(6\hat{i}+6\hat{j}-8\hat{k}\)
3. \(-8\hat{i}-8\hat{j}-6\hat{k}\)
4. \(-6\hat{i}-6\hat{j}-8\hat{k}\)
Subtopic: Lorentz Force |
51%
From NCERT
NEET - 2021
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Ionized hydrogen atoms and \(\alpha\text-\)particles with the same momenta enter perpendicular to a constant magnetic field, \(B\). The ratio of their path radii \(r_{H}:r_\alpha\) will be:
| 1. | \(1:4\) | 2. | \(2:1\) |
| 3. | \(1:2\) | 4. | \(4:1\) |
Subtopic: Lorentz Force |
67%
From NCERT
NEET - 2019
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A metallic rod of mass per unit length of \(0.5\) kgm–1 is lying horizontally on a smooth inclined plane which makes an angle of \(30^\circ\) with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of induction of \(0.25\) T is acting on it in the vertical direction. What is the current flowing through the rod to keep it stationary?
| 1. | \(7.14\) A | 2. | \(5.98\) A |
| 3. | \(14.76\) A | 4. | \(11.32\) A |
Subtopic: Lorentz Force |
58%
From NCERT
NEET - 2018
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An electron is moving in a circular path under the influence of a transverse magnetic field of \(3.57\times 10^{-2}~\text{T}\). If the value of \(\frac{e}{m}\) is \(1.76\times 10^{11}~\text{C/kg}\), what will be the frequency of revolution of the electron?
| 1. | \(1~\text{GHz}\) | 2. | \(100~\text{MHz}\) |
| 3. | \(62.8~\text{MHz}\) | 4. | \(6.28~\text{MHz}\) |
Subtopic: Lorentz Force |
68%
From NCERT
NEET - 2016
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