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ISC Class 12 Moving Charges and Magnetism — practice questions

Explore 133 free Moving Charges and Magnetism questions in ISC Class 12 Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Moving Charges and Magnetism questions and exercises with answers

Showing questions 1–30 of 133.

A point charge moves with velocity v in a region having both an electric field E and a magnetic field B. The total Lorentz force on the charge q is best written as:Read the answer and worked solution →A charged particle is at rest in a region of uniform magnetic field B. The magnetic force acting on it is:Read the answer and worked solution →A positive charge moves with speed v parallel to a uniform magnetic field B. The magnetic force on the charge is:Read the answer and worked solution →A magnetic field B is along the +y axis and a proton moves along the +x axis. The direction of the magnetic force on the proton is:Read the answer and worked solution →The SI unit tesla (T) for magnetic field is equivalent to:Read the answer and worked solution →One gauss equals which of the following in tesla?Read the answer and worked solution →A particle of charge q and mass m moves with speed v perpendicular to a uniform field B, describing a circle. The radius of the circular path is:Read the answer and worked solution →An electron of mass 9 × 10⁻³¹ kg moves at 3 × 10⁷ m s⁻¹. Its kinetic energy, given 1 eV = 1.6 × 10⁻¹⁹ J, is approximately:Read the answer and worked solution →A particle of charge q and mass m undergoes circular motion in a uniform magnetic field B. Its frequency of revolution (cyclotron frequency) is:Read the answer and worked solution →A charged particle moves in a uniform field B such that its velocity has a component v∥ parallel to B. The distance moved along the field in one full revolution (the pitch) is:Read the answer and worked solution →According to the Biot–Savart law, the magnitude of the field dB produced by a current element I dl at distance r, where θ is the angle between dl and r, is:Read the answer and worked solution →The proportionality constant μ₀/4π in the Biot–Savart law has the exact SI value:Read the answer and worked solution →A current element Δl = Δx î (Δx = 1 cm) at the origin carries a current I = 10 A. The magnetic field at a point 0.5 m away on the y-axis has magnitude:Read the answer and worked solution →Using the Biot–Savart law, the magnetic field at the centre of a circular loop of radius R carrying current I is:Read the answer and worked solution →A tightly wound coil of 100 turns and radius 10 cm carries a current of 1 A. The magnitude of the magnetic field at the centre of the coil is:Read the answer and worked solution →A wire carrying current 12 A is bent into a semicircular arc of radius 2.0 cm. The magnetic field at the centre due to the arc is half that of a full loop. Its magnitude is:Read the answer and worked solution →Ampère's circuital law for a closed loop bounding a surface carrying total current I is correctly stated as:Read the answer and worked solution →Using Ampère's law, the magnetic field at a perpendicular distance r from a long straight wire carrying current I is:Read the answer and worked solution →A long straight wire carries a current of 35 A. The magnitude of the magnetic field at a point 20 cm from the wire is:Read the answer and worked solution →The magnetic field inside a long solenoid having n turns per unit length and carrying current I is:Read the answer and worked solution →A solenoid of length 0.5 m and radius 1 cm has 500 turns carrying a current of 5 A. The magnitude of the field inside it is:Read the answer and worked solution →A closely wound solenoid 80 cm long has 5 layers of 400 turns each and carries a current of 8.0 A. The magnitude of B near its centre is approximately:Read the answer and worked solution →Two long parallel wires carry currents in the same direction. The force between them is:Read the answer and worked solution →Two long parallel wires a distance d apart carry currents Iₐ and I_b. The magnitude of the force per unit length between them is:Read the answer and worked solution →The ampere is defined as the steady current which, maintained in two long parallel wires 1 m apart in vacuum, produces a force per metre of length equal to:Read the answer and worked solution →A planar current loop of N turns, area A, carrying current I, has magnetic moment:Read the answer and worked solution →A current loop of magnetic moment m is placed in a uniform field B so that m makes angle θ with B. The torque on the loop has magnitude:Read the answer and worked solution →A current loop of magnetic moment m is placed in a uniform magnetic field B. The net force on the loop is:Read the answer and worked solution →A 100-turn circular coil of radius 10 cm carries a current of 3.2 A. Its magnetic moment is approximately:Read the answer and worked solution →A square coil of side 10 cm with 20 turns carries 12 A. Its normal makes 30° with a uniform horizontal field of 0.80 T. The magnitude of the torque on the coil is:Read the answer and worked solution →

Worked practice questions

A point charge moves with velocity v in a region having both an electric field E and a magnetic field B. The total Lorentz force on the charge q is best written as:

  1. F = q(E + v × B)
  2. F = q(E − v × B)
  3. F = q(B + v × E)
  4. F = q(v × E + B)
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Correct answer: A. F = q(E + v × B)

1. The Lorentz force combines the electric force and the magnetic force on a charge. 2. Electric part: $\mathbf{F}_E = q\mathbf{E}$. 3. Magnetic part: $\mathbf{F}_B = q(\mathbf{v} \times \mathbf{B})$. 4. Adding them: $\mathbf{F} = q[\mathbf{E} + \mathbf{v} \times \mathbf{B}]$. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", p.134_

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A charged particle is at rest in a region of uniform magnetic field B. The magnetic force acting on it is:

  1. Maximum, normal to B
  2. Equal to qB, directed along B
  3. Equal to qB, opposite to B
  4. Zero, since v is zero
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Correct answer: D. Zero, since v is zero

1. The magnetic force is $\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$. 2. Its magnitude is $F = qvB\sin\theta$, which depends on the speed $v$. 3. For a charge at rest, $|\mathbf{v}| = 0$, so $F = 0$. 4. Only a moving charge experiences a magnetic force. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", p.135_

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A positive charge moves with speed v parallel to a uniform magnetic field B. The magnetic force on the charge is:

  1. qvB, perpendicular to v
  2. qvB, directed along v
  3. Zero, as v is parallel to B
  4. Maximum, along B
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Correct answer: C. Zero, as v is parallel to B

1. Magnetic force magnitude: $F = qvB\sin\theta$. 2. When $\mathbf{v}$ is parallel to $\mathbf{B}$, the angle $\theta = 0^\circ$. 3. Then $\sin 0^\circ = 0$, so $F = 0$. 4. The vector product vanishes when velocity and field are parallel. _Source: syllabus Physics Ch 4 "Moving Charges and Magnetism", p.135_

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