Question

Explain how the time it takes to boil a kettle filled with water changes when it is operated from the 120V supply.

Answer 1

Answer:

A voltage V and current I flows then the power dissipated is

P= VI (1)

ohms law so you can calculate the resistance

R = V/ I (2)

if you substitute this expression for I in equation (1) you get:

P = VI = V × V/R = V²/ R .