In an experiment Erin holds two objects. Object A has a net charge of –4.81 × 10–7 C, and object B has a net charge of 6.41 × 10–7 C. She touches the objects together.

(a) Roughly how many more electrons are there than protons in object A before the two objects come in contact?

(b) After Erin touches the objects together, about 5.00 × 1011 electrons transfer from object A to object B. What is the new net charge on object B?

a) object A has electrons more than protons

b)

Explanation:

a)

Electrons are negatively charged particles, so they have a charge of

On the other hand, protons are positively charged particles, so they have a charge of

Therefore, the net charge of an object can be written as

where

is the number of protons

is the number of electrons

So the equation can be rewritten as

Which gives the difference between number of protons and number of electrons.

Here, object A has a charge of

Therefore,

Which means that object A has electrons more than protons.

b)

When Erin touches the objects together, the number of electrons transferred from object A to object B is

The charge corresponding to these electrons transferred is

The initial charge on object B was

This means that the final charge on object B after the electrons are transferred will be: