Resistance & Capacitance

[G1SG2]

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Okay, so these two are constant (kinda), right? Like for resistance, we have V=IR, which gives us R=V/I. However, R is independent of V and I since R can be calculated using R=rho*L/A.

1) So if we have any changes in V or I, do we assume that R does not change? Because any increase in V, for example, will cause a corresponding increase in I, right? And vice versa?

For capacitance, we have C=Q/V. However, C is independent of Q and V because we can calculate capacitance (parallel plate capacitors) using C=KAE0/d.

2) So if we have any changes in Q or V, do we assume that C does not change, since any increase in Q, for example, will cause a corresponding increase in V and vice versa?

Thanks.

 

[Doodl3s]

THat is correct, for example, they might say you have a 2 ohm resistor or a 1uF capacitor... those are its properties...
HOWEVER, for capacitance, the MCAT i've noticed loves doing things like unhooking the capacitor from the voltage source, or changing its distance between the plates.

So basically, resistors are resistors and capacitors have a certain capacitance, however, capacitance can be easily screwed around with unlike resistors... so watch out for them.

 

[G1SG2]

THat is correct, for example, they might say you have a 2 ohm resistor or a 1uF capacitor... those are its properties...
HOWEVER, for capacitance, the MCAT i've noticed loves doing things like unhooking the capacitor from the voltage source, or changing its distance between the plates.

So basically, resistors are resistors and capacitors have a certain capacitance, however, capacitance can be easily screwed around with unlike resistors... so watch out for them.

Okay, got it. So if I get a question saying something like there's a capacitor with charge Q, and the voltage between the plates is V. What will happen to C if Q is halved? even though Q=CV, and Q is halved, nothing will change because C is constant right? The only thing that will happen is that V will be halved (to maintain C)? BUT I can think otherwise if the distance is changed, different dielectrics are inserted, etc, right?