Evans SPH 4U1

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.

Example:

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.