The system is now set up and you will start mapping the electric potential at different points in the Petri dish using the digital multimeter. 17. Turn the multimeter on using the switch under the dial. 18. Put the black probe in contact with the right sphere and the red probe in contact with the left sphere. Observe the reading on the multimeter. 19. Divide the observed reading by six to obtain six even increments. For example, if the observed reading between the two spheres is 2 V, then 0.33, 0.66, 0.99, 1.33, 1.66 and 2 V would be the six equipotential lines you would look for. 20. Find the six equipotentials calculated from Step 19 by holding the black probe on the right sphere and moving the red probe around the field map. 21. After an equipotential has been found, mark its location on the field map in Figure 7b