A student places a chain of two steel paperclips horizontally next to the South (S\text{S}S) pole of a strong bar magnet, as shown in the diagram above. The paperclips become magnetised by magnetic induction.
State the magnetic polarity (North or South) of:
- End 1A (closest to the magnet's South pole).
- End 1B.
- End 2A.
- End 2B.
The student then investigates how the magnetic strength of an electromagnet varies with the electric current flowing through its coil. The electromagnet's strength is measured by finding the maximum mass of iron washers it can lift from a laboratory bench.
The results for the first four test runs are shown in the table below:
| Current / A\text{A}A | Maximum mass of washers lifted / g\text{g}g |
|---|---|
| 0.5 | 12 |
| 1.0 | 24 |
| 1.5 | 36 |
| 2.0 | 48 |
When testing a current of 2.5 A2.5\text{ A}2.5 A, the student obtains the following four repeated measurements:
74 g,61 g,58 g,61 g74\text{ g}, \quad 61\text{ g}, \quad 58\text{ g}, \quad 61\text{ g}74 g,61 g,58 g,61 g
Explain how the student should process these four measurements to find the most accurate representative value for a current of 2.5 A2.5\text{ A}2.5 A.