A student is constructing an investigation on static electricity. The student has three balloons and rubs two of them on a piece of wool. The student then touches each balloon to the wall to observe if static electricity would cause the balloon to stick. What is the independent variable in this investigation.
As given, the student has three balloons and rubs two of them on a piece of wool. The rubbing of balloon on wool is the independent variable as it was done on two and not on the third as control.