6 13142.03 Question 3 Requirements • 3 × 1.5 V cells • 68 Ω resistor in component holder • 3.9 Ω resistor • voltmeter range 0–20V, reading to 0.01 V • milliammeter range 0–200 mA reading to 0.1 mA • connecting wires (8, may vary depending on set up) • 2 × opaque box capable of holding two cells in series Preparation Connect two of the cells in series and place them in a box. Connect a connecting wire to each end of the cells so they protrude from the ends of the box. Label the box ‘Cell A’ and clearly mark the polarity. Connect the remaining cell in series with the 3.9 Ω resistor and place them in the other box. Connect a connecting wire to the open end of the cell and also the open end of the resistor so they protrude from the ends of the box. Label the box ‘Cell B’ and mark the polarity on the box. Label the 68 Ω resistor R. Before the examination Connect ‘Cell A’ and ‘Cell B’ in series and connect the voltmeter across them so it is measuring the e.m.f.. Set the remainder of the apparatus on the bench. Action at Changeover Disconnect the circuit and connect the voltmeter across the cells in series as at the start of the experiment. Check that the e.m.f. is at a value of approx. 4.5 V.