Evans SPH 4U1

Physics Grade 12

Unit 6: Electricity

Note 2: Mini lesson on Charge


Coulomb: We will talk more about later but...its the unit used to measure electric charge. It is equivalent to an excess or deficiency of 6.24 x 1018 electrons.

Charge (q) on one electron is one negative elementary charge =  - 1.6 x 10-19 C

Charge (q) on one proton is one positive elementary charge =  + 1.6 x 10-19 C


Quantity of electric charge:

q = Ne    where q is the quantity of charge in coulombs, N is the # of excess or deficiency of electrons, e is elemental charge.


Example 1:

Calculate the quantity of the electric charge on an object which has an excess of 6.0 x 1030 electrons. ( -9.6 x 1011 C)

Example 2:

Calculate the charge on an electroscope that has a deficiency of 4.0 x 108 electrons. (6.4 x 10-11C)

Example 3:

Calculate the number of excess electrons on a gold leaf electroscope which possesses -4.0 x 10-9 C of electric charge.( 2.5 x 1010 electrons)

Charge Sharing: When charged conductors of equal capacity are brought into contact with each other and then separated, that total charge is shared equally among the conductors.


Three identical spheres, having charges of 5 C, 4 C, and 12 C are brought into contact and then separated. What is the charge on each sphere afterwards?  Solution: Total charge = 21 C  Therefore afterwards the charge on each is 7 C.