The practical voltage source is formed by combining an ideal voltage source (Vs) and internal resistance (r).
1) Without computing, determine sign of power Ps delivered by voltage source
2)Compute Ps delivered by voltage source
3) Compute power Pr absorbed/dissipated in heat by resistor R
4)Compute ratio p=Pr/Ps
5) Find value of R that maximizes p.
6) Assume r << R and compute ratio Pr/PR where Pr is power dissipated by resistor r. Use power balance to determine where power delivered by the voltage source is absorbed
7) Find value of R that maximizes Pr. Compute Pr and p for this value.