020. Electrodynamics (Magnetic field)
Solution
The magnitude of the magnetic field can be obtained from the Biot-Savart law.
$latex B = \\frac{ \\mu_0 I }{ 4\\pi R^2} \\oint dL &s=1$where $latex R$ is the radius of the loop and $latex I$ is the current. In this problem, the radius of the circular loop is $latex a$, the magnitude of the magnetic field at the center of a circular loop is
$latex B = \\frac{ \\mu_0 I }{ 4\\pi a^2} \\cdot (2\\pi a) = \\frac{ \\mu_0 I }{ 2a } &s=1 $
Answer
(D) $latex \\frac{ \\mu_0 I }{ 2a } &s=2$
Reference
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html
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