A portable medical device is powered by a single real battery whose internal resistance cannot be ignored. The battery, of unknown emf ε and internal resistance r, is connected in series with a 220Ω external resistor that models the operating load.
During a test, the current in the circuit is measured to be 0.025A. Simultaneously, a voltmeter connected across the external resistor reads 5.50V.
Use these data to analyze the circuit.
(1) Part 1: Calculate the potential difference across the internal resistance, including its sign.
(2) Part 2: Using your result from part (a), determine the values of the battery emf ε and its internal resistance r.
(3) Part 3: Find the terminal voltage of the battery (the potential difference between its terminals) while the current is 0.025A.
(4) Part 4: Compute the efficiency of power delivery to the external resistor, defined as the ratio of power dissipated in the external resistor to the total power supplied by the battery. Interpret what this efficiency indicates about energy transformations in the device.