Question

Typical blood velocities in the coronary arteries range from 10 to 30 cm/s. An electromagnetic flowmeter applies a magnetic field of 0.22 T to a coronary artery with a blood velocity of 15 cm/s. As we can see in the figure below, this field exerts a force on ions in the blood, which will separate. The ions will separate until they make an electric field that exactly balances the magnetic force. This electric field produces a voltage that can be measured. What force is felt by a singly ionized (positive) sodium ion? ____________ N Charges in the blood will separate until they produce an electric field that cancels this magnetic force. What will be the resulting electric field? _______________ N/C What voltage will this electric field produce across an artery with a diameter of 3.4 mm? ____________ V

Answer 1

a.

F = IqI v B

where,

q = 1.6 x 10^-19 (this is the charge of proton )

v = 0.15 m/s

B = 0.22 T

F = 1.6 x 10^-19 x 0.22 x 0.15

F = 5.28 x 10^21 N

b.

F = qE

E = F/q

E = (5.28 x 10^-21)/ (1.6*10^-19)

E = 0.033 V/m = 3.3 x 10^-2 N/C

c.

3.3 × 10−2 V/m x 0.0034 m = 1.112 x 10^-4 V