capacitor Q based on BRphysic chapter 9_Q12 (p192) &BRphysic chapter 9_Q50 (p202

[blankmoniker]

charge and capacitor question based on BR physic chapter 9 / passage 3 / question 12 (page 192) and BR physic chapter 9 / passage 3/ question 50 (page 202)

would some be able clarify what exactly determines the final charge/voltage on a capacitor? i was under the assumption that a capacitor would be able to obtain less charge (due to less voltage) if there was a resistor (in series) in front of it due to the voltage drop.

i'm now a little confused bc although the explanation listed for Q12 shares my similar reasoning, the explanation for Q50 seem to say otherwise. Q 50's explanation do not take the voltage drop into account bc no current is running through the system. aren't both questions presenting a situation where both of the capacitors are fully charged and would like to know the potential difference across the plates??

thx so much!

Edit: i also realized that on Q56 on BR physic chapter 9 (p203), the key mentions that the maximum charge on the capacitor does not depend on the resistor since Q=VC. but isnt the V across the capacitor dependent on the number of resistors as well?

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[BerkReviewTeach]

charge and capacitor question based on BR physic chapter 9 / passage 3 / question 12 (page 192) and BR physic chapter 9 / passage 3/ question 50 (page 202)

would some be able clarify what exactly determines the final charge/voltage on a capacitor? i was under the assumption that a capacitor would be able to obtain less charge (due to less voltage) if there was a resistor (in series) in front of it due to the voltage drop.

i'm now a little confused bc although the explanation listed for Q12 shares my similar reasoning, the explanation for Q50 seem to say otherwise. Q 50's explanation do not take the voltage drop into account bc no current is running through the system. aren't both questions presenting a situation where both of the capacitors are fully charged and would like to know the potential difference across the plates??

thx so much!

There's a difference between the two circuits and it doesn't jump out at you. In question 12, even after the capacitor is full, there is current going through R1 because of the parallel loop through R3 that bypasses the capacitor. So the voltage across the capacitor is equal to the battery's emf - I1R1.

In question 50, the switch connects to either the capacitor OR the resistor, but not both. This means that when the capacitor is being charged, it is the only circuit element connected to the battery. There is no other voltage drain, so the capacitor gets the full emf of the battery.

Does the difference seem clear?

 

[blankmoniker]

thank you so much for your response- that makes perfect sense!!