A student investigated the relationship between current / and potential difference V for a filament bulb - Leaving Cert Physics - Question 4 - 2017

To create the graph:

1. Label the x-axis as Potential Difference (V) and the y-axis as Current (I in mA).
2. Plot the points based on the provided data, ensuring accuracy in their placement.
3. Draw a smooth curve or straight line (best fit) through the points to represent the relationship.
4. Ensure that the graph is neat and the scales are appropriate.

To calculate resistance at given voltages:

• Ohm's Law: Use the formula: $R = \frac{V}{I}$ .

• At 0.5 V: Determine the corresponding current (I) from the graph. If I = 5.5 mA, then:

  $R = \frac{0.5}{5.5 \times 10^{-3}} = 90.9 \Omega$

• At 8.5 V: Determine the corresponding current (I) from the graph. If I = 121.4 mA, then:

  $R = \frac{8.5}{121.4 \times 10^{-3}} = 70.1 \Omega$

The resistance of the filament begins to change significantly between 4.0 V to 6.0 V based on the observed current changes in the graph.

The resistance of a filament changes with its potential difference due to two main reasons:

1. As potential difference increases, current increases: This leads to an increase in temperature of the filament.
2. As temperature increases, resistance increases: This is due to the increased motion of atoms within the filament which impedes the flow of electrons.