Question

A Faraday ice pail similar to the one you used in lab is shownto the right. As you recall, the principle of its operation relieson the proportionality between the charge on the inner pail and thepotential difference between the inner pail and the ground. Supposethe relationship between charge q and potential difference V isgiven by V=2.5E16 q. When a charged wand is inserted into the innerpail and touches it, the electrometer reading is -18.0 volts. (a)How much charge resided on the wand? (b) Before grounding the pail,a second wand is inserted into the ice pail and touches it. Theelectrometer reading is now +30.0 volts. How much charge resided inthe second wand? (c) If the two wands were separated by 4.0 cmbefore they were discharged onto the ice pail, what force dideither exert on the other? (d) Was it attractive of repulsive?Assume that no leakage of charge occurs during the experiment - allcharge on the wand is transferred to the ice pail when it touchesthe ice pail. Recall that (1/4pi e0)=9E9 Nm2/C2.

The pail looks kind of like this:http://tinyurl.com/6g4g3sv

The answers given by my TA are (a) -7.2E-16C (b) 1.92E-15C(c) -7.77E-18N (d) attractive