In the figure is shown a battery having an emf of 12 Volts and an internal resistance of 0.40 Ohm. A resistor R, of 2.6 Ohms is connected across its terminals ab. Determine (a) resistance of R which, when connected across terminals ab in parallel with R, will make the power delivered by the battery a maximum; (b) current in R, and R; (c) terminal voltage of battery; (d) power in R, and in R; (e) power lost in battery E = 12 V R= 2.6) r = 0.40 S2· Hint: To maximize power in R, use differentiation

Testing a Battery Without a Tester The internal resistance says a lot about the state of the battery. To calculate the actual internal resistance of the battery, MULTIMETER proceed as follows: • Measure the source voltage (voltage when no current is flowing) (Vo) and terminal voltage (voltage when current is flowing) (Vc). CE CAT I Calculate the voltage drop across the internal resistance OFF V 200m 20M (V, - Vo- Vc). CURRENT CLAMP 2. 2M • Measure the load current (1). Calculate the internal resistance (R = V/ I). OFF 20- -200K 1mV/A 200- 20K 10mV/A 600 2K ... A ZERO 10 200 10 COM The battery being tested has a CCA rating of 640 A. The battery manufacturer specifies that the maximum internal resistance should not exceed 2.5 + cold cranking amps (CCA) rating of the battery. What is the maximum acceptable internal resistance value for this battery?