An electrical cartridge heater is embedded inside a small aluminum block. When the heater is switched on, the temperature of the block increases. The table below shows the temperature of the block at regular time intervals.
| Time in seconds | Temperature in ∘C^\circ\text{C}∘C |
|---|---|
| 0 | 20 |
| 10 | 48 |
| 20 | 68 |
| 30 | 80 |
| 40 | 87 |
| 50 | 91 |
| 60 | 93 |
| 70 | 94 |
| 80 | 94 |
| 90 | 94 |
Explain why the temperature of the aluminum block initially rises and then eventually remains at a constant value.