Final answer:
The responding variable in the student's experiment on how voltage affects the current in a circuit is D. The amount of current, as it is the element that changes in response to the different amounts of voltage supplied by the batteries.
Step-by-step explanation:
Identifying the Responding Variable in the Experiment
In this experiment designed by a student to test how changing the amount of voltage affects the current in a series of circuits, the responding variable is the element that changes in response to the manipulation of the independent variable. Since the experiment's purpose is to observe the change in current as a result of varying the voltage supplied by different batteries, the correct answer is D. The amount of current.
The independent variable in this experiment, which is what the student deliberately changes, is the amount of voltage, represented by the use of three different batteries: 1.5V, 3V, and 9V. The resistance and type of circuit are kept constant with three 5.0Ω resistors in series and the use of a series circuit configuration throughout the experiment.
The amount of current is measured as an outcome of these changes, making it the responding variable. Understanding the relationship between voltage, current, and resistance in this way is an application of Ohm's law, which is a fundamental principle in physics and specifically in the study of electric circuits.