A light bulb is connected to a 9 V battery. Predict what will happen to the brightness of the bulb if it is connected to a 1.5 V battery instead. Explain your answer.

As the temperature increases along the x-axis, the resistance also increases along the y-axis. The graph shows a straight line with a positive slope.
The relationship between temperature and resistance is directly proportional (or linear). As temperature increases, resistance increases.

5.2.2)

The independent variable is the one that is changed or controlled in an experiment, typically plotted on the x-axis.
The independent variable is temperature.

The dependent variable is the one that is measured and changes in response to the independent variable, typically plotted on the y-axis.
The dependent variable is resistance.

5.2.3)

The resistance of a conductor is inversely proportional to its cross-sectional area ($R \propto \frac{1}{A}$).
If the conductor is thicker, its cross-sectional area ($A$) increases. Therefore, the resistance would decrease.

The resistance would decrease.