Question

Suppose there exists a third type of charge in addition to the two types we’ve called glass and plastic. Call this third type $X$ charge. What experiment or series of experiments would you use to test whether an object has $X$ charge? State clearly how each possible outcome of the experiments is to be interpreted.

Short answer

If the interactions are such that they can't be explained with the two previously known types (like if the object attracts or repels both the glass and plastic charge), then it must carry some new type of charge that we call$X$

Step-by-step solution

The object repels or attracts the glass and plastic charge

There were two charges that were previously known.

If the object repels both the plastic and glass charges, it must be a different form of charge because neither plastic nor glass are capable of doing so.

If the object repels both the plastic and glass charges, it must be a third sort of charge because neither glass nor plastic can do this.

Glass Charge

If the object attracts the plastic charges but repels the glass charges, we can deduce that it is charged with the glass charge and that no other sort of charge is required to explain the results.

Conclusion

If the object repels the plastic charge but attracts the glass charge, it is simply charged with the plastic charge; there is no need to add a new type of charge.

Take two plastic and glass-charged objects and combine them. Then take the object you want to look at and see if it attracts or repels the plastic and glass charges. If it does, then it must have a new form of charge called $X$.