# Homework Help: Power absorbed by heater

1. Nov 23, 2009

### songoku

1. The problem statement, all variables and given/known data
A heater rated at 2000 W operating at 250 V is used on a supply of 230 V. If the resistance of the heater is independent of temperature, calculate the power absorbed by the heater.

2. Relevant equations
$$P=\frac{V^2}{R}$$

3. The attempt at a solution
resistance of heater :

$$R=\frac{V^2}{P}=31.25~ \Omega$$

The power absorbed :

$$P'=\frac{230^2}{31.25}=1692.8 ~W$$

Do I get it right?

Thanks

2. Nov 23, 2009

### mgb_phys

Yes,
You don't need to actually work out the resistance, you know power is the ratio of the voltage^2
= 2000*(230^2/250^2)

ps. careful about how many significant figures

3. Nov 23, 2009

### songoku

Hi mgb_phys

Ok, thanks a lot !!