Question

the wattage rating W (in watts) of an appliance varies directly with the square of the current I (in amperes) and directly with the resistance R (in ohms). If the wattage is 6 watts when the current is 0.2 ampere and the resistance is 150 ohms, find the wattage when the current is 0.3 ampere and the resistance is 300 ohms.

Answer 1

`P = I\cdot V \text{, where P is power in Watts, I is current and V is in Volts.}`, but

`V = R\cdot I \text{, where V is in Volts, R is resistance and I is current.}`

Doing the math:

`P = I\cdot V`

`P = I\cdot R\cdot I`

`P = R\cdot I^2`

`P = 300^2\cdot 0.3`

`P = 27000`