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Magnetic Field Physics - Magnetic Field

Rajasthan Board (RBSE) - STD 12 Science - Physics (Rajasthan - English Medium). 91 questions in this chapter.

Question types

Magnetic Field question types

91 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

91
Questions
6
Question groups
5
Question types
Sample Questions

Magnetic Field questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
Let $\overrightarrow{\text{E}}$ and $\overrightarrow{\text{B}}$ denote electric and magnetic fields in a frame S and $\overrightarrow{\text{E}}$ and $\overrightarrow{\text{B}}$ in another frame S moving with respect to S at a velocity $\overrightarrow{\text{v}}.$ Two of the following equations are wrong. Identify them.
  1. $\text{B}_\text{y},=\text{B}_\text{y}+\frac{\text{vE}_\text{z}}{\text{c}^2}$
  2. $\text{E}_\text{y},=\text{E}_\text{y}+\frac{\text{vB}_\text{z}}{\text{c}^2}$
  3. $\text{B}'_\text{y}=\text{B}_\text{y}+\text{v}\text{E}_\text{z}$
  4. $\text{E}'_\text{y}=\text{E}_\text{y}+\text{vB}_\text{z}$
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Q 2M.C.Q (1 Marks)1 Mark
A charged particle goes undeflected in a region containing an electric and a magnetic field. It is possible that
  1. $\overrightarrow{\text{E}}||\overrightarrow{\text{B}},\ \overrightarrow{\text{v}}||\overrightarrow{\text{E}}$
  2. $\overrightarrow{\text{E}}$ is not parallel to $\overrightarrow{\text{B}}$
  3. $\overrightarrow{\text{v}}||\overrightarrow{\text{B}}$ but $\overrightarrow{\text{E}}$ is not parallel to $\overrightarrow{\text{B}}$
  4. $\overrightarrow{\text{E}}||\overrightarrow{\text{B}}$ but $\overrightarrow{\text{v}}$ is not parallel to $\overrightarrow{\text{E}}$
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Q 3M.C.Q (1 Marks)1 Mark
An electric current i enters and leaves a uniform circular wire of radius a through diametrically opposite points. A charged particle q moving along the axis of the circular wire passes through its centre at speed v. The magnetic force acting on the particle when it passes through the centre has a magnitude:
  1. $\text{qv}\frac{\mu_0\text{i}}{2\text{a}}$
  2. $\text{qv}\frac{\mu_0\text{i}}{2\pi\text{a}}$
  3. $\text{qv}\frac{\mu_0\text{i}}{\text{a}}$
  4. $\text{Zero}$
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Q 4M.C.Q (1 Marks)1 Mark
A circular loop of area $1\ cm^2,$ carrying a current of $10A,$ is placed in a magnetic field of $0.1T$ perpendicular to the plane of the loop. The torque on the loop due to the magnetic field is :
  • ✓
    Zero
  • B
    $10^4N-m$
  • C
    $10^2N-m$
  • D
    $1N-m$

Answer: A.

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Q 5M.C.Q (1 Marks)1 Mark
Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to a magnetic field?
  • ✓
    Electron
  • B
    Proton
  • C
    $He^+$
  • D
    $Li^+$

Answer: A.

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Q 71 Marks Question1 Mark
Suppose a charged particle moves with a velocity v near a wire carrying an electric current. A magnetic force, therefore, acts on it. If the same particle is seen from a frame moving with velocity v in the same direction, the charge will be found at rest. Will the magnetic force become zero in this frame? Will the magnetic field become zero in this frame?
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Q 91 Marks Question1 Mark
The free electrons in a conducting wire are in constant thermal motion. If such a wire, carrying no current, is placed in a magnetic field, is there a magnetic force on each free electron? On the wire?
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Q 112 Marks Questions2 Marks
A circular coil of radius 2.0cm has 500 turns and carries a current of 1.0A. Its axis makes an angle of 30° with the uniform magnetic field of magnitude 0.40 T that exists in the space. Find the torque acting on the coil.
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Q 132 Marks Questions2 Marks
A wire, carrying a current i, is kept in the x−y plane along the curve $\text{y}=\text{A}\sin\Big(\frac{2\pi}{\lambda}\text{x}\Big).$ A magnetic field B exists in the z direction. Find the magnitude of the magnetic force on the portion of the wire between $\text{x}=0$ and $\text{x}=\lambda.$
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Q 142 Marks Questions2 Marks
The torque on a current loop is zero if the angle between the positive normal and the magnetic field is either $\theta=0^\circ$ or $\theta=180^\circ$ In which of the two orientations, the equilibrium is stable?
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Q 152 Marks Questions2 Marks
A rectangular coil of $100$ turns has length $5\ cm$ and width $4\ cm$. It is placed with its plane parallel to a uniform magnetic field and a current of $2A$ is sent through the coil. Find the magnitude of the magnetic field $B$ if the torque acting on the coil is $0.2\ N m^{-1}.$
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Q 163 Marks Question3 Marks
A particle moves in a circle of diameter $1.0\ cm$ under the action of a magnetic field of $0.40T$. An electric field of $200\ Vm^{-1}$ makes the path straight. Find the charge/ mass ratio of the particle.
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Q 173 Marks Question3 Marks
A proton describes a circle of radius 1cm in a magnetic field of strength 0.10T. What would be the radius of the circle described by an α-particle moving with the same speed in the same magnetic field?
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Q 183 Marks Question3 Marks
A proton is projected with a velocity of $3 \times 10^6 ms^{-1}$ perpendicular to a uniform magnetic field of $0.6T$. Find the acceleration of the proton.
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Q 193 Marks Question3 Marks
A uniform magnetic field of magnitude $0.20T$ exists in space from east to west. With what speed should a particle of mass $0.010g$ and with charge $1.0 \times 10^{-5}C$ be projected from south to north so that it moves with uniform velocity?
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Q 203 Marks Question3 Marks
An experimenter's diary reads as follows: "A charged particle is projected in a magnetic field of $(7.0\vec{\text{i}}-3.0\vec{\text{j}})\times10^{-3}\text{T}.$ The acceleration of the particle is found to be $(\vec{\text{i}}+7.0\vec{\text{j}})\times10\text{m/s}^{2\text{n}}.$ The number to the left of $\vec{\text{i}}$ in the last expression was not readable. What can this number be?
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Q 214 Marks Questions4 Marks
Shows a rod PQ of length 20.0cm and mass 200g suspended through a fixed point O by two threads of lengths 20.0cm each. A magnetic field of strength 0.500T exists in the vicinity of the wire PQ, as shown in the figure. The wires connecting PQ with the battery are loose and exert no force on PQ.
  1. Find the tension in the threads when the switch S is open.
  2. A current of 2.0A is established when the switch S is closed. Find the tension in the threads now.
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Q 225 Marks Questions5 Marks
  1. An electron moves along a circle of radius 1m in a perpendicular magnetic field of strength 0.50T. What would be its speed? Is it reasonable?
  2. If a proton moves along a circle of the same radius in the same magnetic field, what would be its speed?
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Q 235 Marks Questions5 Marks
Doubly$-$ionised helium ions are projected with a speed of $10\ km/s^{-1}$ in a direction perpendicular to a uniform magnetic field of magnitude $1.0T.$ Find
  1. The force acting on an ion.
  2. The radius of the circle in which it circulates.
  3. The time taken by an ion to complete the circle.
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Q 245 Marks Questions5 Marks
A magnetic field of $(4.0\times10^{-3}\vec{\text{k}})$ T exerts a force of $(4.0\vec{\text{i}}+3.0\vec{\text{j}})\times10^{-10}$ N on a particle with a charge of $1.0\times10^{-9}\text{C}$ and going in the x−y plane. Find the velocity of the particle.
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Q 255 Marks Questions5 Marks
A particle with a charge of $5.0\ µC$ and a mass of $5.0 \times 10^{-12}kg$ is projected with a speed of $1.0\ km s^{-1}$ in a magnetic field of magnitude $5.0\ mT.$ The angle between the magnetic field and the velocity is $\sin^{-1} (0.90).$ Show that the path of the particle will be a helix. Find the diameter of the helix and its pitch.
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Q 265 Marks Questions5 Marks
Electrons emitted with negligible speed from an electron gun are accelerated through a potential difference $V$ along the $x-$axis. These electrons emerge from a narrow hole into a uniform magnetic field $B$ directed along this axis. However, some of the electrons emerging from the hole make slightly divergent angles, as shown in the figure. Show that these paraxial electrons are refocussed on the $x-$axis at a distance $\sqrt{\frac{8\pi^2\text{mV}}{\text{eB}^2}}.$
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