- #1

Karol

- 1,380

- 22

## Homework Statement

A 660[W] heater can work on 120[V]. if the voltage decreases to 110[V] what is the power that it consumes?

## Homework Equations

$$V=iR$$

$$P=iV$$

For pure resistance: ##P=i^2R##

## The Attempt at a Solution

The current at 660[W]: ##P=i\cdot 120\rightarrow i=5.5[A]##

The resistance: ##660=5.5^2\cdot R\rightarrow R=22[\Omega]##

The new current: ##V=iR\rightarrow 110=i\cdot 22\rightarrow i=5[A]##

The new power consumption: ##P=i\cdot V=5\cdot 110=550[W]##

And with another method: ##P=i^2\cdot R=5^2\cdot 22=550[W]##

It is written that it should be 500[W]