A group of students is investigating whether copper is a better thermal conductor than steel. The students take a copper wire and a steel wire of the same length and diameter. They put equal lengths of wax on one end of each wire and dip the other end into a beaker of hot water. The length of wax left on the wires after 10 minutes is shown. Experimental Observations Copper Steel Original length of wax 3 cm 3 cm Length of wax after 10 minutes 0.7 cm 1.8 cm What was the dependent variable in this experiment? Type of wire used Original length of wire Original length of wax Thermal conductivity of wire