# Resistive dissipation and Ohm's law

## Homework Statement

A potential difference V is connected across a device with resistance R, causing current i through the device. Rank the following variations according to the change in the rate at which electrical energy is converted to thermal energy due to the resistance, greatest change first:
(a) V is doubled with R unchanged,
(b) i is doubled with R unchanged,
(c) R is doubled with V unchanged,
(d) R is doubled with i unchanged.

## Homework Equations

$$P= {i^2} R$$
$$P= \frac {V^2} R$$

## The Attempt at a Solution

I know and understand that (a) and (b) result in ##P'=4P##, but I'm not sure if I judge (c) and (d) variations correctly. I guess that the answer to (c) and (d) is that there would be no change if the device obeys Ohm's law.

cnh1995
Homework Helper
Gold Member
You can assume some values for V and R and check each condition. You have listed the correct equations.
guess that the answer to (c) and (d) is that there would be no change if the device obeys Ohm's law.
No change in what?

You can assume some values for V and R and check each condition. You have listed the correct equations.

No change in what?
No change in ##P##.

cnh1995
Homework Helper
Gold Member
No change in ##P##.
There will be changes in P according to the equations you've listed.