A student measures the current through a small heating element at different potential differences. Table 1 shows their results.
| Potential difference (V) | Current (A) |
|---|---|
| 1.0 | 0.40 |
| 2.0 | 0.65 |
| 3.0 | 0.80 |
| 4.0 | 0.90 |
| 5.0 | 0.95 |
| 6.0 | 0.95 |
The student uses these results to write the following conclusion:
"As the potential difference across the heating element increases, the current increases and the two variables are directly proportional."
Comment on the student's conclusion.