Electricity

ELECTRICITY

• Electric charge is an electrical property of matter that creates electric and magnetic forces and interactions.
• Like charges repel, and opposite charges attract.
• The two types of charges are called positive and negative.
• An object’s electric charge depends on the imbalance of its protons and electrons.
• Electrons are negatively charged, protons are positively charged, and neutrons are neutral (no charge).
• Negatively charged objects have more electrons than protons.
• Positively charged objects have fewer electrons than protons.
• The SI unit of electric charge is the coulomb, C.
• A proton has a charge of 1.6 ´ 10 –19 C
• An electron has a charge of 1.6 ´ 10 –19 C.
• The net electric charge of a charged object is always a multiple of 1.6 ´ 10 –19 C.
• Conductors allow charges to flow; insulators do not.
• An electrical conductor is a material in which charges can move freely and that can carry an electric current.
• An electrical insulator is a material that does not transfer current easily.
• Objects can be charged by the transfer of electrons.
• The outermost electrons can be easily transferred from one atom to another.
• Charging by friction is when one material gains electrons and becomes negatively charged, and the other loses electrons and becomes positively charged.
• Objects can also be charged without friction.
• One way to charge a neutral object without friction is by touching it with a charged object.
• Objects charged in this manner are said to be charged by contact.
• Charges move within uncharged objects.
• The charges in a neutral conductor can be redistributed without contacting a charged object.
• Although the total charge on the conductor will be zero, the opposite sides will have an induced charge.
• This polarization of the atoms or molecules of an insulator produces an induced charge on the surface of the insulator.

Electric Force

• Electric force is the force of attraction or repulsion between objects due to charge.
• The electric force at the atomic and molecular level is responsible for most of the common forces we can observe.
• The electric force is also responsible for effects that we can’t see.
• Electric force depends on charge and distance.
• The electric force between two objects is proportional to the product of the charges on the objects.
• The electric force is inversely proportional to the square of the distance between two objects.
• Electric force acts through a field.
• An electric field is a region in space around a charged object that causes a stationary charged object to experience an electric force.
• One way to show an electric field is by drawing electric field lines.
• Electric field lines point in the direction of the electric force on a positive charge.
• The electric field lines around a positive charge point outward.
• The electric field lines around a negative charge point inward.
• Electric field lines never cross one another.
• Field lines show both the direction of an electric field and the relative strength due to a given charge.
• More lines are drawn for greater charges to indicate greater force.