20 The semicircular wire of radius R connects two straight wire segments. If a current I follows along the wire, the magnetic field at the center of the semicircular wire due to the current in the semicircular wire is
(A)μ₀I/(2R)
(B)μ₀I/(4R)
(C)μ₀I/(8R)
(D)μ₀I/(2πR)
(E)μ₀I/(4πR)

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