Common static electricity involves charges ranging from nanocoulombs to microcoulombs. (a) How many electrons are needed to form a charge of - 2.00nC (b) How many electrons must be removed from a neutral object to leave a net charge of 0.500µC?

a) 1.24*10¹⁰. b) 3.11*10¹²

Explanation:

The charge is quantized, so any charge is a multiple of the elementary charge e, which is the charge of one electron (being negative) or a proton (if it is positive).

The value of e is 1.61*10⁻¹⁹ coulombs.

a) So, if we need to form a charge of - 2.00 nC, this will be equal to the following expression:

Q = - 2.00 nC = n*e = n * (-1.61*10⁻¹⁹) C

Solving for n, replacing nC by 10⁻⁹ C, we have:

n = - 2*10⁻9 C / - 1.61.10⁻¹⁹ C = 1.24*10¹⁰ electrons.

b) In the same way, we get the number of electrons (as a negative charge) that it is needed to remove from a neutral object to leave a net charge of 0.500 μC = 5*10⁻⁷ C, as follows:

n = - 5*10⁻⁷ C / - 1.61*10⁻¹⁹ C = 3.11*10¹² electrons.