You take two invisible tapes of some unknown brand, stick them together, and discharge the pair before pulling them apart and hanging them from the edge of your desk. When you bring an uncharged...

You take two invisible tapes of some unknown brand, stick them together, and discharge the pair before pulling them apart

and hanging them from the edge of your desk. When you bring an uncharged plastic pen within 10 cm of either the U tape

or the L tape you see a slight attraction. Next you rub the pen through your hair, which is known to charge the pen

negatively. Now you find that if you bring the charged pen within 8 cm of the L tape you see a slight repulsion, and if you

bring the pen within 12 cm of the U tape you see a slight attraction. Briefly explain all of your observations.