Electric Charge and Static Electricity Electric Charge n

Electric Charge and Static Electricity

Electric Charge n Electric charge is a property that causes subatomic particles (protons and electrons) to attract or repel each other. n There are two types of electric charge: n Positive (proton) n Negative (electron)

Electric Charge n An atom is neutral with a positive nucleus and is surrounded by a negatively charged cloud of electrons. n An excess or shortage of electrons produces a net electric charge (ion).

Recap of the Atom

Electric Forces n Like charges repel, and opposite charges attract, this is the law of electric charge. n The attraction or repulsion between electrically charged objects is electric force.

Electric Forces n The electric force between two objects is directly proportional to the net charge of each object. n Electric force decreases as the distance between two objects increases.

Electric Fields n The effect an electric charge has on other charges in the space around it is the charge’s electric field. n The strength of an electric field depends on the amount of charge that produces the field and on the distance from the charge.

Field of a Positive and Negative Charge

Static Electricity and Charging Static electricity is the electric charge which builds up on an object (thus it is not moving and is considered ‘static’). n This charge can be formed by friction, contact (conduction), and induction. n The static charge will eventually move on to another object. This is called electric discharge. n

Static Electricity and Charging n Charges are neither created nor destroyed in the forming of static electricity simply transferred by one of the methods mentioned – friction, conduction or induction.

Charging by Friction n Rubbing two objects together causes friction, which causes a transfer of electrons.

Charging by Conduction n Whenever two objects touch and one of the objects has an electric charge and this charge is transferred or conducted.

Charging by Induction n A transfer of charge without contact between materials. n Charge moves from a charged object to another object through the influence of the first objects electrical field. No charge is actually transferred, the charges within the second object simply rearrange.

Static Discharge n Static discharge occurs suddenly when a pathway for a charged release occurs. n Charges will not travel through air from your hand to the doorknob. The air itself becomes charged suddenly when the gap between your finger and the doorknob is small. Charged air then provides a path for electrons to flow from your hand to the doorknob.

Conductors/Insulators n Electrical conductors are materials which allow charges to move through them. Ex. Metals, salt water, etc. n Electrical insulators are materials which do not allow charges to move through them. Ex. Rubber, glass, wood, etc.