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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Magnetic Field

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Magnetic Field

A rectangular coil comprising 100 turns has a length of 5 cm and a...

A rectangular coil comprising 100100 turns has a length of 5 cm5 \text{ cm} and a width of 4 cm4 \text{ cm}. It is positioned such that its plane is parallel to a uniform magnetic field, and a current of 2 A2 \text{ A} is passed through the coil. Determine the magnitude of the magnetic field BB if the torque acting on the coil is 0.2 N m−10.2 \text{ N m}^{-1}.

Options

  1. A50 T50 \text{ T}
  2. B0.25 T0.25 \text{ T}
  3. C5×10−5 T5 \times 10^{-5} \text{ T}
  4. D0.5 T0.5 \text{ T}

Correct answer

D. 0.5 T0.5 \text{ T}

Step-by-step solution

The torque acting on a current-carrying coil in a uniform magnetic field is given by:

τ=NIABsin⁡θ\tau = N I A B \sin\theta

Given that the plane of the coil is parallel to the magnetic field, the angle between the area vector and the magnetic field is \theta = 90^{}^{{}^{\circ}}.

Substituting the given values:

N=100N = 100

I=2 AI = 2 \text{ A}

A=5 cm×4 cm=20 cm2=20×10−4 m2A = 5 \text{ cm} \times 4 \text{ cm} = 20 \text{ cm}^2 = 20 \times 10^{-4} \text{ m}^2

τ=0.2 N m\tau = 0.2 \text{ N m}

We get:

0.2 = 100 \times 2 \times 20 \times 10^{-4} \times B \times \sin(90^{}^{{}^{\circ}})

0.2=4000×10−4×B0.2 = 4000 \times 10^{-4} \times B

0.2=0.4×B0.2 = 0.4 \times B

B=0.20.4=0.5 TB = \dfrac{0.2}{0.4} = 0.5 \text{ T}
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