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Force On A Moving Charge In Magnetic Field - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main
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Force on a moving charge in magnetic field is considered one of the most asked concept.
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61 Questions around this concept.
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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 along the direction of the fields with a certain velocity, then
A particle of mass M and charge Q moving with velocity $\vec{v}$ describes a circular path of radius $R$ when subjected to a uniform transverse magnetic field B. The work done by the field when the particle completes one full circle is
A negative test charge is moving near a long straight wire carrying a current. The force acting on the test charge is parallel to the direction of the current. The motion of the charge is :
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In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a:
At a specific instant, the emission of the radioactive compound is deflected in a magnetic field. The compound can emit
The emission at the instant can be
In a certain region, static electric and magnetic fields exist. The magnetic field is given by $\overrightarrow{\mathrm{B}}=\mathrm{B}_0(\hat{i}+2 \hat{j}-4 \hat{k})$. If a test charge moving with a velocity $\vec{v}=v_0(3 \hat{i}-\hat{j}+2 \hat{k})$ experiences no force in that region, then the electric field in the region, in SI units, is :
Direction : In the following question, a statement of Assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
Assertion : Work done by magnetic field on a moving change is zero.
Reason : Force experienced by moving charge in a magnetic field may be zero.
The negatively and uniformly charged nonconducting disc as shown in the figure is rotated clockwise with great angular speed. The direction of the magnetic field at point A in the plane of the disc is
An electron enters a chamber in which a uniform magnetic field is present as shown. Ignore gravity.
During its motion inside the chamber
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Force on a moving charge in magnetic field
Force on a moving charge in magnetic field:
The magnetic force on a free moving charge is perpendicular to both the velocity of the charge and the magnetic field with direction given by the right hand rule. The force is given by the charge times the vector product of velocity and magnetic field.
The force is always perpendicular to both the magnetic field and velocity.
$
\begin{aligned}
& F=q v B \sin \theta \\
& F=q v B \text { if } \theta=90
\end{aligned}
$
If the velocity is perpendicular to the magnetic field then the force is given by the simple product :
$
\text { Force }=\text { charge } \times \text { velocity } \times \text { B-field }
$
Right hand rule: speed $v$ in a magnetic field of strength $B$ is given by
$
F=q v B \sin \theta,
$
the tesla ( T ). Therefore magnetic field strength is given as :
$
B=\frac{F}{q v \sin \theta}
$
The unit of tesla is :
$
1 \mathrm{~T}=\frac{1 \mathrm{~N}}{\mathrm{C} \cdot \mathrm{~m} / \mathrm{s}}=\frac{1 \mathrm{~N}}{\mathrm{~A} \cdot \mathrm{~m}}
$
- The direction of the force on a moving charge is given by right hand rule. Point the thumb of the right hand in the direction of $v$, the fingers in the direction of $B$, and a perpendicular to the palm points in the direction of $F$.
- The force is perpendicular to the plane formed by $\boldsymbol{v}$ and $\boldsymbol{B}$. Since the force is zero if $\boldsymbol{v}$ is parallel to $\boldsymbol{B}$, charged particles often follow magnetic field lines rather than cross them.
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