EXAMPLE 2–1 An initially neutral body has 1.7 mC of negative charge
removed. Later, 18.7 1011 electrons are added. What is the body’s final
charge?
Solution Initially the body is neutral, i.e., Qinitial 0 C. When 1.7 mC of
electrons is removed, the body is left with a positive charge of 1.7 mC. Now,
18.7 1011 electrons are added back. This is equivalent to
18.7 1011 electrons 0.3 mC 1 coulomb
6.24 1018 electrons
of negative charge. The final charge on the body is therefore Qf 1.7 mC
0.3 mC 1.4 mC.
To