How to culculate rms current using Watts in a Household Curcuit

[jmmckiss]

Homework Statement

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?

Homework Equations

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

I= q/t V= W/q

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.

 

[Sunil Simha]

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

 

[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!

 

[CWatters]

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

 

[Nickie]

I would first clarify some missing information in the problem. Without the time variable, it is not possible to calculate the current (I) using the given equation I=q/t. This equation requires the charge (q) and time (t) to be known. Additionally, the voltage (V) is also needed to use Ohm's law (V=IR) to calculate the resistance (R).

In a household circuit, the voltage is typically 120V, so I will assume this value for the rest of my explanation. Using the given power (P) and voltage (V) for each lamp, we can calculate the current (I) using the equation P=VI.

For Lamp 1: I=150W/120V = 1.25A
For Lamp 2: I=150W/120V = 1.25A
For Lamp 3: I=100W/120V = 0.83A

To calculate the resistance (R) of each bulb, we can rearrange Ohm's law to R=V/I. Using the calculated currents for each lamp, we get:

For Lamp 1: R=120V/1.25A = 96Ω
For Lamp 2: R=120V/1.25A = 96Ω
For Lamp 3: R=120V/0.83A = 144Ω

It is important to note that these calculations assume the bulbs are connected in parallel, meaning they each have the same voltage across them (120V). If they were connected in series, the voltage would be divided between them and the calculations would be different.

In conclusion, the current (I) and resistance (R) for each bulb in the household circuit can be calculated using the given power (P) and voltage (V) values. However, it is important to clarify any missing information and understand the circuit configuration before attempting these calculations.