Resistance, Capacitance,

In summary, the conversation revolves around a circuit with a voltage source and a capacitor, and various questions about its behavior when the source is removed. The initial and final voltages and charges are calculated using equations and the values for resistance and capacitance, and the capacitors are identified as being in series or parallel depending on the presence or absence of the voltage source.
  • #1
thenewbosco
187
0
this seems to be a simple question
for the diagram at http://img.photobucket.com/albums/v11/biggm/ohm.jpg [Broken]

a)the circuit has been connected a long time...what is the voltage across the capacitor?

this one i calculated and got the right answer of 6V.

b)if the battery is disconnected how long does it take to discharge the capacitor to 1/10 of its initial voltage.

i have the equation t=-RC ln (q/Q)

where R= resistance, C=capacitance, q= final charge and Q=initial charge, i have calculated the initial and final charges using q=CV and final voltage of 3/5V. Capacitance is given...what value do i use for resistance?
i can see given the answer that it should be 18/5...which is the product of the initial and final voltage although this could be coincidental...any help here??
 
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  • #2
With the voltage source removed and the capacity supplying the voltage, which capacitors are in series?
 
  • #3
the 1ohm and 4 ohm are in series, and the 8ohm and 2ohm are in series.
do i just add these as in series and then...if i add them together as two then in parallel it does not work out...
 
  • #4
The 1 and 4 ohm resistors are in series and the 1 and 8 ohm resistors are with respect to the 10V source.

However when 10V source is removed and the capacitor provides the potential difference, resistors 4 and 2 ohm are then in series and resistors 1 and 8 ohm are in series.
 
  • #5
ah thanks for that tip...it works out now but i fail to see how the 4 and 2 combination and the 1 and 8 ohm combination are in series when the potential is removed.
 
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  • #6
Some quick photoshopping reveals

http://img299.imageshack.us/img299/1403/untitled14xz.gif [Broken]
 
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What is resistance?

Resistance is the measure of an object's ability to resist the flow of electrical current. It is measured in ohms (Ω) and is influenced by factors such as the material, length, and thickness of the object.

What is capacitance?

Capacitance is the ability of an object to store electrical charge. It is measured in farads (F) and is influenced by factors such as the distance between the plates and the dielectric material between them.

What is the relationship between resistance and current?

According to Ohm's law, the relationship between resistance and current is inverse. This means that as resistance increases, current decreases, and vice versa.

What is the relationship between capacitance and voltage?

The relationship between capacitance and voltage is direct. This means that as capacitance increases, voltage also increases, and vice versa.

How are resistance and capacitance related in a circuit?

Resistance and capacitance are both important factors in determining the behavior of a circuit. They can affect each other, as well as other components, and can be used together to control the flow of current and voltage in a circuit.

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