A closely wound solenoid of 2000 turns and area of cross-section 1.5 × 10^ -4 ~m^2 carries a current of 2.0 ~A . It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal

Correct answer: C. 1.5 × 10^ -2 ~N -m Given, N=2000, ~A=1.5 × 10^ -4 ~m^2i=2.0 AB=5 × 10^ -2 ~T , and θ=30^ ^ Torque, = NiBA θ aligned & =2000 ×2 ×5 ×10^ -2 ×1.5 ×10^ -4 × 30^ ^ & =2000 ×50 ×10^ -6 × (1)/(2) & =1.5 ×10^ -2 Nm aligned

NEET 2010

Exam: NEET
Year: 2010
Subject: Physics
Chapter: Magnetic Effects of Current

NEET 2010 · Physics · Magnetic Effects of Current

A closely wound solenoid of 2000 turns and area of cross-section...

A closely wound solenoid of 2000 turns and area of cross-section

1.5 \times 10^{-4} \mathrm{~m}^2

carries a current of

2.0 \mathrm{~A}

. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field

5 \times 10^{-2} \mathrm{~T}

making an angle of

30^{\circ}

with the axis of the solenoid. The torque on the solenoid will be

Options

A $3 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
B $1.5 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
C $1.5 \times 10^{-2} \mathrm{~N}$ -m
D $3 \times 10^{-2} \mathrm{~N}-\mathrm{m}$

Correct answer

C. $1.5 \times 10^{-2} \mathrm{~N}$ -m

Step-by-step solution

Given,

\mathrm{N}=2000, \mathrm{~A}=1.5 \times 10^{-4} \mathrm{~m}^2\mathrm{i}=2.0 \mathrm{AB}=5 \times 10^{-2} \mathrm{~T}

, and

\theta=30^{{}^{\circ}}

Torque,

\tau=

NiBA

\sin \theta

\begin{aligned}& =2000 \times2 \times5 \times10^{-2} \times1.5 \times10^{-4} \times \sin30^{{}^{\circ}} \\ & =2000 \times50 \times10^{-6} \times \frac{1}{2}\\ & =1.5 \times10^{-2} \mathrm{Nm} \end{aligned}

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