# Circuit Related

1. Mar 21, 2005

So I did a couple circuit questions and these two really have me stumped. One is on paye 613 of The cutnell physics sixth edition number 36. or:

(one star)
A light bulb is connected to a 120.0V wall socket. The current in the bbulb depends on the time t according to the relation I=(0.707 A)sin[(314HZ)t]
a) what is the frequency of the alternating current
b) determine the resistance of the bulb's filament
c) what is the average power consumbed by the light bulb?

from my guesses i believe you use P=I^2R and V/I=R kinds of formulas as well as P=V^2rms/R and P=I^2rmsR to solve bits and pieces but i dont know how to use time and alternating current to deal with this question... in fact i cant even approach this. can someone help me out?

The other question is 92. page 616 (one star)
A 3.00 mF and a 5.00 mF capacitor are connected in series across a 30.0V battery. A 7.0 mF capacitor is then connected in parallel across the 3.00 mF capacitor. Determine the volatage across the 7.00 mF capacitor.

with this question i just generally have no freaking CLUE how to do this other than the capacitors in series and capacitors in paralell equations.... i really dont have any idea... help would be appreciated.

2. Mar 22, 2005

the second question horrifies me beyond repair.... it looks so easy... but it isnt..? series is in reciprocal and parallel is in regular right....?

i think i got a 10V drop on the second question over the 7. but i'm not sure......

3. Mar 22, 2005

ok solved the second one... that i thought was harder. can someone help wiht the first? i need to know part b and c.

4. Mar 22, 2005

### VinnyCee

A little help...

For capacitors in series, the Voltage V across each can be found with $$V_1 = \frac{q}{C_1}$$ and these add up to $$30 V = V_1 + V_2$$.

Hope this helps a little