Grade 9 Science Exam Review - Solutions 2014 | страница 6

Electricity Review 1. a) All matter is made up of atoms. The three subatomic particles that make up an atom are protons, electrons and neutrons b) Two types are charges are negative and positive. Negative charges are caused by an excess of electrons. Positive charges are caused by a deficit of electrons. c) The law of electric charges states: i) Negative charges repel negative charges ii) Positive charges repel positive charges iii) Positive charges attract negative charges d) Complete the following table: Method of Description of Process Charging Friction See Textbook Contact Induction (Temporary) Final charge on Objects Transfer of Electrons + or - Some See Textbook + or - Some See Textbook Neutral None 2. a) A conductor is a conductor of electrons. An example of a good conductor is copper. b) An insulator is a poor conductor of electrons. An example of a good insulator is wood. 3. a) To ground an object simply connect a wire to the ground. b) Discharging objects is easier when the air is dry. c) Four ways to discharge an object are: i) discharge at a point ii) connect to ground Page 6 of 17