Two balloons are rubbed with wool, giving each a negative charge. The balloons are then attached to a table using tape and string, as shown below.
Which of the following actions will increase the electric potential energy between the two balloons?
A.
releasing both balloons into the air
B.
bringing the two balloons closer together
C.
adding two inches to the length of both strings
D.
separating the two balloons
B. bringing the two balloons closer together
By bringing the two balloons closer together, the distance between them decreases, which increases the electric potential energy between them. This is because the force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. So, decreasing the distance increases the force, and thus the potential energy.