A pupil performed an experiment on a resistor to investigate the relationship between potential difference (voltage) applied to the resistor and the current flowing through the resistor - Junior Cycle Science - Question c - 2009

To calculate the resistance (R) of the resistor, we can use Ohm's Law, which states:

$R = \frac{V}{I}$

Using the highest values from the data:

• Potential difference, V = 5 Volts
• Current, I = 0.25 Amperes

Thus, the resistance is:

$R = \frac{5 \text{ V}}{0.25 \text{ A}} = 20 \text{ Ohms}$

The evidence that potential difference (voltage) is directly proportional to current is illustrated by the graph showing a straight line through the origin. This indicates that as voltage increases, the current also increases in a linear fashion, confirming the proportionality.