Final answer:
The use of armor rods requires attaching the conductor at the midpoint of the armor rod. For charging by induction, the object must be a conductor. Simply touching two polarized insulating objects together does not cancel the polarization, and insulators like wood can conduct electricity under certain conditions like in a lightning strike.
Step-by-step explanation:
When using armor rods in electrical engineering, the conventional wisdom is to attach the conductor to the insulator at the midpoint of the armor rod. This is typically done to ensure that the strain is distributed evenly along the length of the armor rod, providing stability and reducing the risk of damage to the conductor. However, the context of the question and the conductors in question suggest that there might be a specific scenario or use case being referred to that isn't fully detailed in the question provided.
In the context of the question regarding the charging of a sphere by induction, it is accurate to say that the sphere must indeed be a conductor in order for induction to occur. Insulators do not allow for the free movement of charges on their surface, and hence cannot be charged by induction.
Regarding the polarization of two insulating objects, simply touching them together will not necessarily cancel the polarization. Polarization is a rearrangement of charges within an object, and connecting two polarized insulating objects does not allow charges to move freely between them to neutralize the polarization.
It is also true that materials typically known as insulators, such as wood, can conduct electricity under certain circumstances, such as during a lightning strike. Therefore, lightning can travel through a tree to reach the Earth.