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Question: Answered & Verified by Expert
A wire of mass $100 \mathrm{~g}$, length $1 \mathrm{~m}$ and current $5 \mathrm{~A}$ is balanced in mid air by a magnetic field $B$, then find the value of $B$.
PhysicsMagnetic Effects of CurrentAIIMSAIIMS 2012
Options:
  • A $0.2 \mathrm{~T}$
  • B $0.1 \mathrm{~T}$
  • C $0.5 \mathrm{~T}$
  • D $0.6 \mathrm{~T}$
Solution:
1354 Upvotes Verified Answer
The correct answer is: $0.2 \mathrm{~T}$
Here, $m=100 \mathrm{~g}=10^{-1} \mathrm{~kg}, l=1 \mathrm{~m}, I=5 \mathrm{~A}$ For a wire balanced midway air by a magnetic field is
$m g=I l B$
or $B=\frac{m g}{I l}$
$=\frac{10^{-1} \times 10}{5 \times 1}$
$B=0.2 \mathrm{~T}$

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