Question

A metal sphere has no charge on it. A positively charged object is brought near, but does not touch the sphere. Show that this object can exert a force on the sphere even though the sphere has no net charge. How can you test your answer experimentally?

Answer 1

A neutral metal sphere can be affected by a nearby charged object through electrostatic induction, which redistribits charges within the sphere. This phenomenon creates electrostatic forces between the sphere and the object and can be demonstrated using an electroscope.

Step-by-step explanation:

Electrostatic Induction and Forces on a Neutral Sphere

A neutral metal sphere can indeed be affected by a nearby charged object due to a process called electrostatic induction. This occurs when the electric field emanating from the charged object causes a redistribution of charges within the neutral sphere. In the presence of a positively charged object, electrons within the sphere will be attracted toward the side nearest to the charged object, creating a negative region while leaving a positive region on the far side. The sphere still has no net charge, but it has now effectively separated charges internally due to the induced polarization. This separation of charge creates an electrostatic force between the sphere and the nearby charged object.

To test this experimentally, one could use an electroscope. By bringing a charged rod near to a neutral metal sphere connected to an electroscope, one can observe the leaves of the electroscope diverging, indicating an induced charge. If the charged object is then removed while the leaves remain diverged, it shows that the electrostatic force was indeed affecting the sphere without direct contact.