Constants ? Part A Typical blood velocities in the coronary arteries range from
ID: 1731960 • Letter: C
Question
Constants ? Part A Typical blood velocities in the coronary arteries range from 10 to 30 cm/s. An electromagnetic flowmeter applies a magnetic field of 0.25 T to a coronary artery with a blood velocity of 15 cm/s As we see in the figure, this field will exert 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. (Figure 1) What force is felt by a singly ionized (positive) sodium ion? Submit Part B Charges in the blood will separate until they produce an electric field that cancels this magnetic force. What will be the resulting electric field? In Figure 1 of 1 Submit PartC What voltage will this electric field produce across an artery with a diameter of 3 mm? Express your answer using two significant figures.Explanation / Answer
(a) As the ion is moving in a magnetic field, it will experience a magnetic force given as
F = qvB
where q is charge, v is velocity and B is magnetic field.
For a proton, q = 1.6e-19 C (positive charge)
Therefore,
F = 1.6e-19 C * 0.15 m/s * 0.25 T
F = 6e-21 N
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(b) Relating magnetic field and electric field, we have
F = qE
E = F/q
E = 6e-21 N / 1.6e-19 C
E = 0.0375 V/m
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(c) The voltage produced due to this electric field
V = Ed
V = 0.0375 V/m * 3e-3 m
V = 1.125e-4 Volts
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