Final answer:
The charge on an electrophorus will decrease when it touches one terminal of a capacitor, as some of its charge gets transferred to the capacitor plates.
Step-by-step explanation:
When an electrophorus touches one terminal of a capacitor, the charge on the electrophorus will decrease. This is because the positively charged electrophorus will donate some of its excess electrons to one of the plates of the capacitor, which is how it gets charged. Upon contact, electrons will transfer from the electrophorus to the capacitor until the potential difference is equalized. The overall effect is a reduction in the excess charge initially present on the electrophorus.
Considering the principles of electrostatics, when a charged insulator, like a glass rod, touches a conductor, such as an electroscope or an electrophorus, electrons are transferred, leaving the conductor with a net charge. Because capacitors store charge on their plates, touching one plate with a charged object will transfer some of the charge onto the plate, altering the charge on the originally charged object, in this case, the electrophorus.
Thus, the correct answer is that the charge on the electrophorus will decrease upon touching the terminal of a capacitor.