- #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]