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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Magnetic Field due to a Current

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Magnetic Field due to a Current

A circular loop with a radius of 20 cm carries a 10 A current. An...

A circular loop with a radius of 20 cm20 \text{ cm} carries a 10 A10 \text{ A} current. An electron passes through the centre of the loop, crossing its plane at a speed of 2.0×106 m s−12.0 \times 10^6 \text{ m s}^{-1}. If the electron's direction of motion is at a 30^{}^{{}^{\circ}} angle to the axis of the circle, determine the magnitude of the magnetic force acting on the electron at the moment it crosses the plane.

Options

  1. A8π×10−19 N8\pi \times 10^{-19} \text{ N}
  2. B16π×10−19 N16\pi \times 10^{-19} \text{ N}
  3. C32π×10−19 N32\pi \times 10^{-19} \text{ N}
  4. D163π×10−19 N16\sqrt{3}\pi \times 10^{-19} \text{ N}

Correct answer

B. 16π×10−19 N16\pi \times 10^{-19} \text{ N}

Step-by-step solution

The magnetic field at the centre of a circular loop is given by B=μ0I2RB = \dfrac{\mu_0 I}{2R}

Substituting the given values:

B=4π×10−7×102×0.2=π×10−5 TB = \dfrac{4\pi \times 10^{-7} \times 10}{2 \times 0.2} = \pi \times 10^{-5} \text{ T}

The direction of this magnetic field is along the axis of the circular loop.

The magnitude of the magnetic force acting on the electron is given by F=qvBsin⁡θF = qvB \sin\theta

Substituting the values of charge, velocity, magnetic field, and angle:

F = (1.6 \times 10^{-19}) \times (2.0 \times 10^6) \times (\pi \times 10^{-5}) \times \sin 30^{}^{{}^{\circ}}

F=1.6×10−19×2.0×106×π×10−5×12F = 1.6 \times 10^{-19} \times 2.0 \times 10^6 \times \pi \times 10^{-5} \times \dfrac{1}{2}

F=1.6π×10−18 N=16π×10−19 NF = 1.6\pi \times 10^{-18} \text{ N} = 16\pi \times 10^{-19} \text{ N}
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