Electric field treatments and electroporation
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Electric field treatments and electroporation
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[ID] => 558268
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[post_date] => 2025-01-09 07:58:01
[post_date_gmt] => 2025-01-09 12:58:01
[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
Electric Field Treatment (EFT) is a relatively recent innovation in medicine that allows for the electric polarization of patient tissue in a clinical setting. This procedure is particularly useful on a molecular level. For example, EFT can be used to rearrange charges on the cell membrane, resulting in an induced transmembrane potential. It can also be used to excite or inhibit voltage-gated ion channels, which can be useful in treating patients with intracellular sodium deficiency.
One researcher is interested in utilizing EFT to deliver drugs through electroporation. This process involves temporarily permeabilizing the membrane through brief exposure to an electric field. To begin her study, she sets up two large metal plates separated by a distance D are charged using a battery of voltage V. This creates a region of uniform and constant electric field throughout the region between the plates. Various charges (either + or -) can then be shot downward through the region at the midway point between the plates.
Figure 1. A diagram of the experiment apparatus.
Source: Schoenbach, K. Stark, R. Jingdong, D. Aly, R. Beebe, S. Buescher, E. (2000). Biological/medical pulsed electric field treatments. Power Modulator Symposium. Norfolk, VA, USA.
[post_title] => Electric field treatments and electroporation
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[question] => If negatively charged particles are shot downwards out of the particle injector, their motion would best be described as which of the following?
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[answer] => 1
[description] => Reason for the Correct Answer:
Positive charges create electric fields that point away from them, negative charges create electric fields that point towards them.
Since the right side of the battery is the positive side, since it has the larger line, the right plate is a positive plate.
The right plate will create a field the points to the left, and the left plate will create a field that points to the left.
Negative charges feel a force in the opposite direction of the electric field, so the electrons would feel a force to the right.
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[answers] => Array
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[0] => Array
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[each_answer] => A. The negative charges would veer to the right
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[1] => Array
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[each_answer] => B. The negative charges would veer to the left
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[2] => Array
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[each_answer] => C. The negative charges would continue straight through the region without deflection
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[3] => Array
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[each_answer] => D. The negative charges would stop and turn around heading back towards the charge injector
)
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => The experimenters want to increase the degree of deflection of the particles, causing them to get deflected more from their initial direction. Which of the following would NOT increase the deflection of the particles?
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[answer] => 3
[description] => Reason for the Correct Answer:
Increasing the charge increases the force causing more deflection.
Decreasing the separation of the plates increases the electric field, and therefore the force causing more deflection.
Increasing the voltage of the battery will increase the electric field between the plates, which increases the force, and therefore the deflection.
Increasing the mass of the injected particles will increase their inertia, causing them to deflect less from their initial direction.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Increase the charge of the injected particles
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[1] => Array
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[each_answer] => B. Increase the voltage of the battery
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[2] => Array
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[each_answer] => C. Increase the mass of the injected particles
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[each_answer] => D. Decrease the separation between the plates
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => Two trials are conducted with identical particles. In the first trial particles are injected at a lower speed, and in the second trial particles are sent through the region with a larger speed. What would be the most likely comparison between the two trials reported by the experimenters?
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[answer] => 1
[description] => Reason for the Correct Answer:
Electric force does not depend on speed.
The voltage of the battery will not change significantly due to a fast moving particle near it.
Since the faster particles are moving faster, they spend less time in the region between the plates, and therefore the same electric force has less time to act on them, deflecting them less.
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[answers] => Array
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[0] => Array
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[each_answer] => A. The particles with larger speed would be deflected less since they spend less time in the region between the plates
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[1] => Array
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[each_answer] => B. The particles with larger speed would be deflected less since the electric force on them would be smaller
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[2] => Array
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[each_answer] => C. The particles with larger speed would be deflected more since the electric force on them would be larger
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[each_answer] => D. The particles with larger speed would be deflected more since the voltage in the region would be larger
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[3] => Array
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[quiz_unique_key] => 2261298308
[question] => For the particles that are deflected, which of the following can be said for sure?
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[answer] => 3
[description] => Reason for the Correct Answer:
The particles could be + or they could be -.
The electric field points toward lower electric potential.
All charges feel a force towards lower electric potential energy, so the particles would get deflected towards lower electric potential energy.
)
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[0] => Array
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[each_answer] => A. The particles deflect towards higher electric potential
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[1] => Array
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[each_answer] => B. The particles deflect towards lower electric potential
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[each_answer] => C. The particles deflect in such a direction as to decrease their electric potential energy
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[each_answer] => D. The particles deflect in such a direction as to increase their electric potential energy
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[quiz_unique_key] => 574431310
[question] => If the charge of one of the injected particles is doubled, how would the force on that particle change?
[value] => Array
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[answer] => 3
[description] => Reason for the Correct Answer:
The electric force on a charge is given by the formula F=qE.
E is constant since we aren’t changing the battery or separation between the plates.
Since E is constant, doubling q will double the force F.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. The electric force would quadruple
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[1] => Array
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[each_answer] => B. The electric force would not change
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[2] => Array
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[each_answer] => C. The electric force on the charge would double
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[each_answer] => D. The electric force would get cut in half
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[558268|1] => A
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[558268|3] => A
[558268|4] => C
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