AAMC Self Assessment Physics #58

[sanguinee]

I'm having a little difficulty understanding this and would really appreciate it if someone could explain ti to me.

"Which will occur when the magnet used in a flowmeter is replaced with a stronger magnet?"
a. electric field will reverse polarity
b. electric field will decrease
c. voltage will increase
d. blood will flow faster

C is apparently the right answer because stronger B field increases the magnetic force which leads to an increase in the voltage (across in artery).

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[sanguinee]

SOS where are my physics majors at

 

[TheOneAndOnlyJamesFranco]

A loose version of the answer is (I vaguely remember this passage so I apologize for its generality):

Think of the electric force and the magnetic force working in conjunction to equilibrate the charged particles in the artery.. so if the magnetic force is increased than to get back to equilibrium you need to also increase electric force.

Sort of like the Milikan oil drop expt.

 

[everydayeddy]

I looked at this problem using the passage and the equation V=Ed since the artery is acting like 2 parallel plates. E is the electric field strength which is due to the segregation of charges. The segregation of charges is due to the magnetic forces pulling negative and positive charges to opposite sides. This is caused by the magnetic field impart by the magnet.

So the stronger the magnet the stronger the magnetic forces. The stronger the magnetic forces the stronger the segregation of charges occur. So the stronger the segregation of charges the stronger the Electric field.

So remember V=Ed, since E is increasing, the value for V(voltage) increases.

BONUS: if you have a stronger Magnet this means a stronger Magnetic field. So v(velocity)=V(voltage)/Bd will decrease the velocity of your blood. At equilibrium.