Suppose Sumana forgets to move the switch of her lifting electromagnet model to OFF position (in introduction story). After some time, the iron nail no longer picks up the iron paper clips, but the wire wrapped around the iron nail is still warm. Why did the lifting electromagnet stop lifting the clips? Give possible reasons.
The lifting electromagnet stopped lifting the clips because the electric cell became weak or dead after being connected for a long time.
The chapter explains that when a cell is used continuously, the chemicals inside get used up over time, and the cell stops working.
However, some current was still flowing through the wire (enough to cause heating but not enough to create a strong magnetic field), which is why the wire remained warm. The cell was not completely dead but had weakened significantly.
Explanation
The chapter explains that in a Voltaic cell, over time, the chemicals get used up, and the cell stops working. It is then called 'dead' and cannot supply any more electricity. In this case, the cell was left connected for an extended period, causing it to weaken. The heating effect requires less current than the magnetic effect needed to lift clips, so the wire was still warm but the electromagnet was too weak to attract the clips.
Solution Steps
The electric cell became weak or dead after being connected for a long time
When a cell is used continuously, the chemicals inside get used up over time
Some current was still flowing through the wire, enough to cause heating but not enough to create a strong magnetic field
The heating effect requires less current than the magnetic effect needed to lift clips