D and E please

(20%) Problem 1: In order to measure the properties of a battery, several resistors are connected to the battery in series and the terminal voltage is measured. In the first case, the resistor has resistance R/ = 2.5 2 and the terminal voltage is AV1 = 2.8 V. In the second case, the resistor has resistance R2 = 71 2 and the terminal voltage AV2 = 6.5 V. 20% Part (a) Express the current through a battery I using the voltage across the terminal AV and the resistance of the circuit R. 1 = AV/R Correct! 20% Part (b) Express the emf of the battery using the variables for current I, internal resistance r, and external resistance R. E = I (r+ R) Correct! 20% Part (c) Express the emf in terms of r, R and 4V. & = AV/R (R + r)