7-1 Electric Charge You will be learning: 1.To describe how electric charges exert forces on each other. 2.How to compare the strengths of electric and gravitational forces. 3.To distinguish between conductors and insulators. 4.How objects become electrically charged.

Positive and Negative Charge Protons have positive charge. Electrons have negative charge. Atoms lose electrons making the atom positively charged. The loose electrons are negatively charged. Static electricity is the accumulation of excess electric charge on an object.

Law of conservation of Charge: charge can be transferred from object to object, but cannot be created or destroyed. Electric field surrounds every electrical charge that causes other electrical charges to be attracted or repelled. Electrical forces is much stronger than the force of gravity. (4 forces of nature)

Conductors Conductor is a material that allows electrons to move easily. Metals are good conductors because the electrons are held together loosely in a “sea of electrons”.

Insulator A material in which electrons do not move easily. Glass, wood, rubber

Charging Objects A object becomes charged when losing electrons due to friction. Charging by contact: transferring charge by touching or rubbing. Charging by inductions: the rearrangement of electrons on a neutral object caused by a nearby charged object. Remember: there are always loose electrons

Lightning: massive static discharge caused by the friction of air molecules. Air is always moving trying to balance the temperature. Producing air temperatures of 30,000 0 C. Thunder is the sound waves given off as the heat produced by the lightning causes air in the bolt’s path of expand rapidly. Grounding is the connection of an object to the Earth. Earth is a large neutral object that can transfer excess electrons.

Detecting Electric Charge Electroscope –Has two metal leaves at the end of a metal rod. –When neutral the leaves hang straight. –When the leaves are charged the leaves repel each other ( since they have the same charge).

A ____ allows electrons to move freely. CONDUCTOR

Gravity is a stronger force than electricity. A.True B.False

Alike charges _____. REPEL

Opposite charges _____. ATTRACT