# Homework Help: What is resistance of a DC circuit has resistor n capacitor connect parallel

1. Nov 19, 2008

### Learner123

1. The problem statement, all variables and given/known data

the title says everything, any formula that to find resistance in a DC circuit of one resistor and one capacitor connect parallel, as well as the current through each of R and C (the known values are R C and V)

2. Relevant equations

seem to me i = (V/R)e^ (-e/RC), but it only say for series
3. The attempt at a solution

couldn't find answer in text and on any website

2. Nov 19, 2008

### Hootenanny

Staff Emeritus
3. Nov 19, 2008

### Learner123

does that mean the current won't go through capcitor branch? and that means if i want to find resistance of the circuit, it's simply R?(nothin to do with C)
and wat about time constant? T = RC? will it be the same like when capacitor n resistor connect series?

Last edited: Nov 19, 2008
4. Nov 19, 2008

### Hootenanny

Staff Emeritus
It means that after a very short time interval, no current will pass through the capacitor branch, all the current will flow through the resistor.

5. Nov 19, 2008

### Learner123

what about time constant T = RC, will it be zero also?

6. Nov 19, 2008

### Hootenanny

Staff Emeritus
There is no time-constant in this case since after the initial current spike through the capacitor branch, the circuit simply behaves like a a resistor connected across a potential difference.

7. Nov 19, 2008

### Learner123

thanx a lot, that quite a lot info for me

8. Nov 19, 2008

### Hootenanny

Staff Emeritus
No problem. If you need to we can treat the network more rigorously, so if you have any more questions please feel free to return.

9. Nov 20, 2008

### jdstokes

What happens if we remove the resistor so the circuit consists just of a charged capacitor? Going around the loop we get $q/C = 0$ so q = 0 (i.e., it discharges immediately). Hmm.

10. Nov 20, 2008

### Hootenanny

Staff Emeritus
That is indeed the case.

11. Nov 20, 2008

### naresh

Which is why you should be careful while shorting capacitors in the lab