Circuit Potential and Voltage Calculations

[triplezero24]

1. For http://www.pen.eiu.edu/~cuemc4/circuit.bmp picture.. Calculate the potential at point D.

2. I 15-V battery is connected to three capacitors in series. The capacitors have the following capacitances: 4.5microFarads, 12.0microFarads, and 32microFarads. Find the voltage across the 32microFarad capacitor.

I am so lost.

 

[triplezero24]

Please? I'm desperate!

 

[learningphysics]

I couldn't open your first picture... I get a "server not found" message.

For the second one... first find the equivalent total capacitance (combine 3 capacitors in series). The find the total charge on this equivalent capacitor.

You should then be able to get the charge on each capacitor (hint: this is really simple... if you are unsure read your textbook regarding combining series and parallel capacitors), and then get the voltage on each capacitor.

 

[triplezero24]

http://www.pen.eiu.edu/~cuemc4/circuit.bmp

That might work. Mak sure you're soomed in all the way or it won't look right. Thanks for the help so far!

 

[learningphysics]

New link doesn't work either.

 

[triplezero24]

I'll attatch it.

 

[learningphysics]

Hmmm... absolute potential can't be calculated unless there's ground assigned somewhere. But I don't see one on the circuit. Are you sure the question asks for potential at D and not potential difference between 2 different points? Does the question mention about 0 volts being assigned somehwere?

 

[triplezero24]

Sorry. It says point A is grounded (V=0).

 

[learningphysics]

ok cool. So first find the current I in the circuit using KVL. So then you can get all the voltage drops across all the resistors (voltage drop across a resistor=current*resistance). Using that you should be able to find the potential at D. Be careful with signs!

Hope this helps!