Effects of voltage on capacitance?

[MikeMitchell]

Encountered a question during a practice exam that I don't understand the answer to. The goal is to increase the capacitance in a circuit containing a voltage source and a resistor (Everything is in series). Two answers seem correct to me, one being by increasing the area of the plates (the correct answer). I also though that replacing the resistor with one of lower resistance value would increase the capacitance since V=IR and C=Q\V. Wouldn't lowering the resistance lower the voltage in the circuit, and in turn increase the capacitance?

thanks so much for any help!

Possibly just figured this out typing out the question. The voltage is set by the source and altering the resistance will only have an effect on I (current), which has no effect on capacitance. Hmm..

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[gunj122]

yea, what you said at the end answers what you asked at the top lol

 

[justhanging]

Encountered a question during a practice exam that I don't understand the answer to. The goal is to increase the capacitance in a circuit containing a voltage source and a resistor (Everything is in series). Two answers seem correct to me, one being by increasing the area of the plates (the correct answer). I also though that replacing the resistor with one of lower resistance value would increase the capacitance since V=IR and C=Q\V. Wouldn't lowering the resistance lower the voltage in the circuit, and in turn increase the capacitance?

thanks so much for any help!

Possibly just figured this out typing out the question. The voltage is set by the source and altering the resistance will only have an effect on I (current), which has no effect on capacitance. Hmm..

Lowering the resistance won't lower the voltage in the circuit. The voltage in the circuit is set by the battery. Lowering the resistance would increase the voltage in the capacitor, I believe. The capacitor will have higher voltage so its charge Q would increase. Capacitance says the same.

 

[gunj122]

Lowering the resistance won't lower the voltage in the circuit. The voltage in the circuit is set by the battery. Lowering the resistance would increase the voltage in the capacitor, I believe. The capacitor will have lower voltage so its charge Q would increase. Capacitance says the same.

lowering the resistance would not increase the voltage. based of Ohm's law, V=IR, voltage and resistance are directly proportional. lowering resistance, however, will increase current.

 

[Rabolisk]

Lowering the resistance won't lower the voltage in the circuit. The voltage in the circuit is set by the battery. Lowering the resistance would increase the voltage in the capacitor, I believe. The capacitor will have higher voltage so its charge Q would increase. Capacitance says the same.

The capacitor will not have higher voltage, because all of the voltage drop will be at the capacitor, rather than the resistor. There will be no current through the resistor once the capacitor is fully charged, and thus no voltage drop through the resistor. A chance in resistance will only affect the rate at which the capacitor is charged, but not its capacitance, final voltage, or final charge.