You rub a rod of glass with a cotton cloth, then dip the cloth into a Faraday pail like we will be using in lab. Will a charge sensor connected to the pail give a negative reading, or a positive reading or will it read essentially zero?

negative charge

Explanation:

As the glass rod is rubbed with the cotton cloth, then the glass rod becomes positively charged and the cotton cloth becomes negatively charged.

There is a tendency to lose the electrons by the glass rod and to grab the electrons by the cotton cloth.

So, the sensor shows negative charge.