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Magnetic Field Physics - Magnetic Field

Bihar Board (BSEB) - STD 12 Science - Physics (BSEB - 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 [1M]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 2M.C.Q [1M]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 3M.C.Q [1M]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 [1M]1 Mark
A circular loop of area 1cm2, 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:
  1. Zero
  2. 104N-m
  3. 102N-m
  4. 1N-m
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Q 5M.C.Q [1M]1 Mark
Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to a magnetic field?
  1. Electron
  2. Proton
  3. He+
  4. Li+
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Q 71 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 91 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 11Short Answer Type Questions [2M]2 Marks
A rectangular coil of 100 turns has length 5cm and width 4cm. 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 0.2N m-1.
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Q 12Short Answer Type Questions [2M]2 Marks
Assume that the magnetic field is uniform in a cubical region and is zero outside. Can you project a charged particle from outside into the field so that the particle describes a complete circle in the field?
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Q 14Short Answer Type Questions [2M]2 Marks
A semicircular wire of radius 5.0cm carries a current of 5.0A. A magnetic field B of magnitude 0.50T exists along the perpendicular to the plane of the wire. Find the magnitude of the magnetic force acting on the wire.
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Q 15Short Answer Type Questions [2M]2 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 163 Marks Question3 Marks
A straight wire of length l can slide on two parallel plastic rails kept in a horizontal plane with a separation d. The coefficient of friction between the wire and the rails is $\mu.$ If the wire carries a current i, what minimum magnetic field should exist in the space in order to slide the wire on the rails?
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Q 173 Marks Question3 Marks
A particle moves in a circle of diameter 1.0cm 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 183 Marks Question3 Marks
A proton is projected with a velocity of 3 × 106 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 × 10-5C 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 22Long Answer Type Questions [5M]5 Marks
A narrow beam of singly charged potassium ions of kinetic energy 32keV is injected into a region of width 1.00cm with a magnetic field of strength 0.500T, as shown in the figure. The ions are collected at a screen 95.5cm away from the field region. If the beam contains isotopes of atomic weights 39 and 41, find the separation between the points where these isotopes strike the screen. Take the mass of a potassium ion = A (1.6 × 10-27)kg, where A is the mass number.

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Q 23Long Answer Type Questions [5M]5 Marks
Two particles, each with mass m are placed at a separation d in a uniform magnetic field B, as shown in the figure. They have opposite charges of equal magnitude q. At time t = 0, the particles are projected towards each other, each with a speed v. Suppose the Coulomb force between the charges is switched off.
  1. Find the maximum value vm of the projection speed, so that the two particles do not collide.
  2. What would be the minimum and maximum separation between the particles if $\text{v}=\text{v}_{\text{m}}\sqrt{2}?$
  3. At what instant will a collision occur between the particles if v = 2vm?
  4. Suppose v = 2vm and the collision between the particles is completely inelastic. Describe the motion after the collision.

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Q 24Long Answer Type Questions [5M]5 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 25Long Answer Type Questions [5M]5 Marks
Doubly-ionised helium ions are projected with a speed of 10km/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 26Long Answer Type Questions [5M]5 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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