Problem 2
A DC source of emf E and internal resistance r supplies a purely resistive load R in series; take E and r as constant and the leads ideal. The circuit reaches steady current, the terminal voltage is U, and useful power is delivered to the load. (a) Express current and load voltage in terms of R. (b) Find the load R for maximum power and that maximum. (c) Find efficiency there, defined as load power divided by the power supplied by the ideal emf. Use SI units throughout and treat components as ideal exactly as specified. State sign conventions when writing equations and retain units in final results.
problems.proof.stepOf
problems.proof.analysis
First identify the system, given quantities, and sign convention; this determines what is conserved or acts on the body. The stated idealizations exclude unmentioned forces or effects.