Question

Two identical metal balls are suspended by insulating threads. What will happen if one of the balls is positively charged?

1) The balls will repel each other
2) The balls will attract each other
3) The balls will remain stationary
4) The balls will fall to the ground

Answer 1

When two metal balls are in contact and exposed to a negatively charged rod, one will become positively charged and the other negatively charged due to electrostatic induction. If the second, negatively charged, ball is grounded, it loses its excess negative charge to the Earth.

Step-by-step explanation:

When two identical metal balls are suspended, and one is positively charged, the effects between the two can be quite interesting. If one ball becomes positively charged, and they are in contact with each other when introduced to a negatively charged rod:

• Ball 1 will gain a positive charge and Ball 2 will gain a negative charge.
• The presence of the negatively charged rod induces redistribution of charge, causing electrons to be transferred from Ball 1 to Ball 2, making Ball 1 positive and Ball 2 negative due to electrostatic induction.
• If Ball 2 is momentarily grounded while under the influence of the charged rod, the excess electrons will flow to the ground, leaving it neutral or slightly charged, depending on the strength of the influence from the rod.

In general, when two objects are charged and brought into contact, the electrons will move to balance out the charges. If both objects are conductors like metal spheres, this redistribution occurs until both objects achieve an equilibrium state, where the total charge is evenly distributed between the two.