Question

You have two identical neutral metal spheres labeled A and B, mounted on insulating posts, and you have a plastic pen that charges negatively when you rub it on your hair (Figure 14.77).

(a) (+ and −) Explain in detail, including diagrams, what operations you would carry out to give sphere A some positive charge and sphere B an equal amount of negative charge. (b) (+ and +) Explain in detail, including diagrams, what operations you would carry out on the neutral spheres to give sphere A some positive charge and sphere B an equal amount of positive charge (the spheres are initially uncharged).

Short answer

(a) When the pen is brought near to A then it will get positively charged and B will get negatively charged due to induction.

(b) When a negatively charged pen is brought near the neutral spheres then, they will get positively charged.

Step-by-step solution

the Significance of the induction charging for spheres

Charging by induction states that an uncharged particle can get charged if it is kept beside a charged particle.

Also, induction charging is a process in which charging an object without touching the object is grounded on a “neutrally charged material”.

The induction charging gives the operations needed to charge both the spheres A and B.

Determination of the operations needed for giving sphere A, a positive charge and sphere B, a negative charge

(a)

The diagram for explaining the operations is shown below-

Initially, both the bodies are neutral, after rubbing, one sphere gets one type of charge and another sphere gets an opposite charge of the same amount. However, this is possible due to the fact of charging by induction. So, when a negatively charged pen is brought near sphere A, then it gets positively charged, and when the pen is brought near sphere B, then it gets negatively charged due to the fact of induction.

Thus, when the pen is brought near to A then it will get positively charged and B will get negatively charged due to induction.

Determination of the operations needed for giving positive charge to both the spheres

(b)

The diagram for explaining the operations is shown below,

In this case, the spheres will be kept at some distance to avoid induction and the pen will bring near both of them to make them positively chargedwith an equal amount of charge due to the fact of induction.

Thus, when a negatively charged pen is brought near the neutral spheres then, they will get positively charged with an equal amount of charge.