Moving Charges and Magnetism - Result Question 51
52. At what distance from a long straight wire carrying a current of $12 A$ will the magnetic field be equal to $3 \times 10^{-5} Wb / m^{2}$ ?
(a) $8 \times 10^{-2} m$
(b) $12 \times 10^{-2} m$
(c) $18 \times 10^{-2} m$
(d) $24 \times 10^{-2} m$
[1995]
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Answer:
Correct Answer: 52. (a)
Solution:
- (a) Current (I) $=12 A$ and magnetic field (B) $=3 \times 10^{-5} Wb / m^{2}$. Consider magnetic field $\vec{B}$ at distance $r$.
Magnetic field, $B=\frac{\mu_0 I}{2 \pi r}$
$\Rightarrow r=\frac{\mu_0 I}{2 \pi B}=\frac{(4 \pi \times 10^{-7}) \times 12}{2 \times \pi \times(3 \times 10^{-5})}=8 \times 10^{-2} m$
