Q4: As in Example 28.2, consider a power supply with fixed emf e and internal resistance r causing current in a load resistance R. In this problem, R is fixed and r is a variable. The efficiency is defined as the energy delivered to the load divided by the energy delivered by the emf.
(a) When the internal resistance is adjusted for maximum power transfer, what is the efficiency?
(b) What should be the internal resistance for maxi- mum possible efficiency?
(c) When the electric com- pany sells energy to a customer, does it have a goal of high efficiency or of maximum power transfer? Explain.
(d) When a student connects a loudspeaker to an amplifier, does she most want high efficiency or high power transfer? Explain.