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## Homework Statement

Thermal energy is to be generated in a 0.31 resistor at the rate of 11 W by connecting the resistor to a battery whose emf is 2.1 V.

(a) What potential difference must exist across the resistor?

(b) What must be the internal resistance of the battery?

## Homework Equations

P = IV

V = IR

## The Attempt at a Solution

I tried manipulating the variables and substituting in the equations. P =IV, 11 = IV, V= IR, 11=I^2*R, 11=I^2*.31, so i divided 11/.31 then took the square root, which was about 6 for the current. I went back and multipled V=IR, to find V=6*.31 , which was 1.86 V. I thought that to find the total potential difference i had to add the emf V given and the V i found from current and resistance, which was 1.86V + the 2.1 V emf... 3.96. But this answer is incorrect.

As for part B, i'm completely lost.