Two cells are connected in series with their emfs aiding each other as shown. Cell A has emf E1=1.5V and internal resistance r1=0.3Ω. Cell B has emf E2=2.0V and internal resistance r2=0.2Ω. The series combination is connected to an external resistor R=4.0Ω.
(i) Write the loop equation for the circuit and calculate the current through R.
(ii) Determine the potential difference across the external resistor.
(iii) Calculate the power dissipated in each cell’s internal resistance.
(iv) The two cells are now re-connected so that their emfs oppose each other (terminals reversed for one cell) while all other values remain the same. Find the current through R in this case and state its direction with respect to the assumed positive direction in part (i).