# Homework Help: How to culculate rms current using Watts in a Household Curcuit

1. Mar 25, 2013

### jmmckiss

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

Three lamps are connected in a household curcuit. Lamps 1 and 2 have 150W bulbs and lamp 3 has a 100W bulb. What is the Current (I) and Resistance (R) of each bulb?

2. Relevant equations

V=IR P = W/t = (V*q)t = V*I

I= q/t V= W/q

3. The attempt at a solution

Lamp 1
V=150W*1.6*10^-19 C?

i'm not sure how to do this exactly. my teacher didn't explain very thoroughly. No time variable is given, no voltage, or current. I don't know how I can use Ohm's law.

2. Mar 25, 2013

### Sunil Simha

Can you assume standard household voltage ( like in India it is 220V rms)?

3. Mar 27, 2013

### jmmckiss

YEp!

I can assume a voltage, for the US household curcuot it's 120 V, and I can plug that into the P=VI to get my answer.Thanks!!

4. Mar 28, 2013

### CWatters

Just for info - It can't be done any other way. You have to know the voltage.