Electricity Unit

An electric charge is a negative or positive amount of electricity that builds up in an object.

On many common objects the electric charge stays in the same place in which the rubbing action took place. Because the electric charge is staying still it is said to be “static”.

Static electricity is a charge on a substance that stays in the same place. Electrostatics is the study of static electric charge.

Electric Charge There are two kinds of electric charges: negative and positive. When two neutrally charged objects are rubbed together, one substance always becomes positively charged while the other object becomes negatively charged.

Law of electric charges states that like charges repel one another and unlike charge attract one another. Law of Electric Charges

How do objects become electrically charged?

There are three ways in which objects become electrically charged: by friction, by contact and by induction.

Friction is a rubbing action that can cause an electric charge to be transferred from one object to another. Friction causes many of the effects produced by static electricity.

The Electrostatic Series A list called the electrostatic series is used to determine the kind of electric charge (positive or negative) produced on each substance when any two substances on the list are rubbed together.

Acetate Glass Wool Cat’s fur, Human hair Calcium, Magnesium, Lead Silk Aluminum, Zinc Cotton Paraffin Wax Ebonite Polyethylene (plastic) Carbon, Copper, Nickel Rubber Sulfur Platinum, Gold Weaker Hold on electrons Increasing Tendency To Gain Electrons (become negatively charged) Stronger Hold on electrons

Charge by Contact is when an already charged object touches another object with a lesser charge or a neutral charge, the extra electrons in the charged object transfer to the object with the lesser charge.

Example: You walk across a carpet floor with sock feet and become electrically charged, then you touch a doorknob (neutrally charged) you feel a shock. This shock is the sharing of electrons between you and the doorknob.

Charge by Induction: a method used to charge an object without actually touching the object to any other charged object. Electrons shift their position on an object to produce opposite charges on either side of the object

Conductors and Insulators An electrical conductor is a substance in which electrons can move freely from one atom to another. An electrical insulator is a substance in which electrons cannot move freely from one atom to another.

Good Conductors Silver Copper Gold Aluminum Magnesium Tungsten Nickel Mercury Platinum Iron

Good Insulators Oil Fur Silk Wool Rubber Porcelain, Glass Plastic Wood, Paper Wax