A student investigates the efficiency of a miniature electric water pump used to raise water.
The measurements recorded during their single trial are shown in the table.
| Measurement | Value |
|---|---|
| Current in pump motor | 1.5 A |
| Potential difference across pump | 6.0 V |
| Volume of water transferred | 500 cm3 |
| Time taken to pump water | 15.0 s |
Which of these changes would improve the reliability of the results?
Repeating the measurements and calculating a mean value
Using a power supply with a higher potential difference
Carrying out the experiment with different volumes of water
Raising the upper beaker to a higher level