Question

Gina examines the equations for electric power and Ohm's law. She thinks that there is a third equation that can calculate power using only voltage and resistance. Which statement best evaluates Gina’s idea?

It is correct, because I = . It is correct, because I = .

It is incorrect, because both equations for power use current.

It is incorrect, because Ohm’s law does not include I2.

Answer 1

The correct answer is the first one.

Answer 2

There are some missing details in the options given, but we can solve the problem anyway.

In fact, the formula for the electric power is

`P=I^2 R`
where I is the current and R the resistance, while Ohm's law states that

`I= (V)/(R)`
where V is the voltage. So, if we replace the current I in the first equation by using Ohm's law, we can write the power using only voltage V and resistance R:

`P= ((V)/(R))^2 R= (V^2)/(R)`