試題詳解

49. One way to measure blood flow when blood vessels are exposed during surgery is to use an
electromagnetic flowmeter. The device surrounds the blood vessel with an electromagnet to
create a magnetic field perpendicular to the blood flow. Since blood is a modest conductor, a
motional emf develops across the blood vessel. Given the vessel diameter d, magnetic field B,
and voltage V measured across the vessel, what is the volume flow rate of blood?
(A) πdV⁄(4B)
(B) πdV⁄(2B)
(C) πdV⁄B
(D) 2πdV⁄B
(E) 4πdV⁄B