MCAT Physics Question — AED
- Nov 12, 2014
- MCAT Blog, MCAT Physics, MCAT Question of the Day
- Reviewed By: Liz Flagge
An automatic external defibrillator (AED) is simply a series of capacitors used to store a very large charge, which is then discharged through the patient’s chest in a short time. If the capacitor in an AED is fully charged and the AED is no longer connected to the power source, what will happen to the energy stored in the AED if the dielectric (κ = 1.5) is removed?
A) increase by a factor of 1.5
B) increase by a factor of 2.25
C) decrease by a factor of 1.5
D) decrease by a factor of √1.5
The MCAT will expect you to know a handful of equations for capacitors. The three needed to solve this question are:
C = κεoA / d
C = Q / V
PE = (½)QV
According to the first equation, we see that if the dielectric is removed, capacitance will decrease by a factor of 1.5.
According to the second equation, we see that a decreased capacitance can either be the result of a change in Q or a change in V. In this question, the AED is no longer connected to the battery, so there is no source of additional charges. Thus Q will remain the same and V will increase by a factor of 1.5
Finally, by the third equation we see that if V is increased by a factor of 1.5, the potential energy will increase by a factor of 1.5. Thus (A) is the correct answer.
Want more MCAT practice?
We’ve got options for every schedule and learning style!
From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!
Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT Advisor using the form below. No obligation, just expert advice.
Search the Blog
Free ConsultationSchedule Now
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More