Final answer:
To determine the sign of an unknown charge on the gold leaf, you can use the process of induction by bringing a charged object close to the gold leaf without touching it.
Step-by-step explanation:
In order to determine the sign of an unknown charge on the gold leaf using either one of the two strips, you can use the process of induction. This involves bringing a charged object close to the gold leaf without touching it. If the gold leaf is repelled, it indicates that the charge on the strip is the same as the charge on the object. If the gold leaf is attracted, it indicates that the charge on the strip is opposite to the charge on the object.