A student measures the current through a newly developed conducting polymer filament at various potential differences. Table 1 shows their results.
| Potential difference (V) | Current (mA) |
|---|---|
| 0.5 | 1.2 |
| 1.0 | 2.4 |
| 1.5 | 3.3 |
| 2.0 | 3.8 |
| 2.5 | 4.0 |
| 3.0 | 4.0 |
The student uses these results to write the following conclusion:
"Since doubling the potential difference from 0.5 V to 1.0 V doubles the current, the current is directly proportional to the potential difference across the entire range, and it continues to increase throughout."
Comment on the student's conclusion.