A researcher investigates the magnetic properties of three separate metal rods, labeled A, B, and C. Each rod is made of a different material from the following list:
- copper
- soft iron
- hard steel
Each rod is placed inside a solenoid that is connected to a direct current (DC) power supply and a switch. The magnetic flux density (BBB) is measured using a sensitive magnetic probe aligned with the axis of the rod, as shown in the diagram below.
The table below shows the magnetic flux density (BBB) measured near the end of each rod at different stages of the experiment:
| Rod | Magnetic flux density before current is switched on / mT | Magnetic flux density when there is a current in the coil / mT | Magnetic flux density 10 seconds after current is switched off / mT | Magnetic flux density 5 minutes after current is switched off / mT |
|---|---|---|---|---|
| A | 0.0 | 0.0 | 0.0 | 0.0 |
| B | 0.0 | 120.5 | 1.1 | 0.0 |
| C | 0.0 | 85.0 | 81.5 | 81.2 |
Complete the table below to identify the material each rod is made from and provide the scientific reason why.
One row (Rod A) has been completed for you.
| Rod | Material | Reason |
|---|---|---|
| A | Copper | It is non-magnetic because its magnetic flux density remains at 0.0 mT under all conditions, meaning it cannot be magnetised. |
| B | ||
| C |