Magnetic Effects Of Current Question 90
Question: An electric current passes through a long straight wire. At a distance 5 cm from the wire, The magnetic field is B. The field at 20 cm from the wire would be [CPMT 2001; Pb PET 2002]
Options:
A) $ \frac{B}{6} $
B) $ \frac{B}{4} $
C) $ \frac{B}{3} $
D) $ \frac{B}{2} $
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Answer:
Correct Answer: B
Solution:
$ B={{10}^{-7}}\frac{2i}{r}\Rightarrow \frac{B}{{{B}’}}=\frac{20}{5}\Rightarrow {B}’=B/4 $
BETA
