Final answer:
When plastic is rubbed with cat fur, it becomes negatively charged due to the transfer of electrons from the fur to the plastic, which has a higher affinity for electrons.
Step-by-step explanation:
The nature of charge produced on plastic when rubbed with cat fur is a negative charge. This occurs because during the rubbing process, electrons are transferred from one material to another based on their affinity for electrons. In this case, plastic has a higher affinity for electrons than cat fur, resulting in the plastic rod becoming negatively charged. This happens because friction causes a slight separation of charges, with the material that has a greater affinity for electrons (plastic in this instance) gaining negative charge, while the other material (cat fur) is left with a positive charge.