8.1 and 8.2

resistance

The amount of current in a circuit also depends on the resistance of the material through which it travels. Resistance is the measure of how difficult it is for charges to flow through a material. The greater the resistance, the less current there is for a given voltage. The unit measure of resistance is the ohm.

charging by induction

charging by induction is a movement of electrons to one part of an object that is caused by the electric field of a second object. The electric field around the charged object attracts or repels electrons in the second object.

the four factors affecting resistance

temperature, diameter, length, and material

factors affecting resistance: diameter

More electrons can flow through a thicker material. As diameter (or thickness) increases, resistance decreases. Thin wires have less resistance than thick ones.

what is a closed circuit

A closed circuit is one in which the pathway of electric current is complete an unbroken.

law of conservation of charge

According to this law, a charge can be transferred from object to object. Although, like the law of conservation of mass it can not be created nor destroyed. The charge simply moves from one place to another.

static electricity

An electron can sometimes leave their atoms. An uncharged object becomes charged by gaining or losing electrons. If an object loses electrons, it has an overall positive charge. If an object gains electrons it has an overall negative charge. The buildup of charges on an object is called static electricity. Static means "not moving or changing." In static electricity, charges build up on an object, but they don't flow continuously.

what is a open circuit

An open circuit is one in which the pathway of electric current is broken. A switch is a device in the circuit in which the circuit can be closed (turned on) or open (turned off).

factors affecting resistance: temperature

Atoms and electrons move more at higher temperatures, so flowing electrons "collide" more often with other electrons and nuclei at higher temperatures. As temperature increases resistance decreases.

voltage

Charges in an electric circuit flow because of a difference in electrical potential energy. The difference in electrical and potential energy between two places in a circuit is called the potential different, or voltage. The unit measure of voltage is the volt (V). Voltage causes a current in an electric circuit. You can think of voltage as the amount of force pushing an electric current. An electric circuit also required a source of energy, such as a battery, to maintain voltage. A voltage source is a device that creates a potential different in an electric circuit.

charging by conduciton

Charging by conduction is the transfer of electrons from a charged object to another by direct contact.

charging by fricition

Charging by friction is the transfer of electrons from on uncharged object to another by rubbing.

conductor

Conductor- Electric charges do not flow easily through every material. A conductor transfer electric charge well. An insulator does not transfer electric charge well. Metals such as silver, copper, aluminum, and iron are good conductors. A conductor is a material through which charge can easily flow. As charges flow through a conductor, they form an electric current. Conductors are used to carry electric charge.

direct current vs. alternating current

Direct current is electrical current which comes from a battery which supplies a constant flow of electricity in one direction. Alternating current is electrical current which comes from a generator.

thunder and lighting

During thunderstorms, air swirls violently. Water droplets within the clouds become electrically charged. To restore a neutral condition in the clouds, electrons move from areas of negative charge to areas of positive charge and produce an intense spark. Some lighting reaches Earth because charges at the bottom of storm clouds may cause the surface of the Earth to become positively charged by induction. Electrons jump between the cloud and Earth's surface, producing a giant spark to travel through the air. This is possible because of charging by conduction.

factors affecting resistance: length

Electrons have to travel farther in a longer wire. As length increases, resistance increases. Long wires are more resistant than short.

static discharge

If an object gains a static charge, the object doesn't hold the charge forever. When a negatively charged object and a positively charged object are brought together, electrons transfer until both objects have the same charge. The loss of static electricity as electric charges transfer from on object to another is called static discharge.

transferring charges

If an object gives up electrons, another object gains those electrons. There are three methods by which charges can be transferred to build up static electricity: charging by friction, by conductions, and by induction.

insulator

Insulator-A material through which charges cannot flow easily is called an insulator. Rubber, glass, sand, plastic, and wood are all examples of good insulators.

factore affecting resistance: material

Insulators have high resistance and conductors have low resistance.

what is an electric feild

It extends around a charged object. An electric field is a region around a charged object where the objects electric force is extended on other charged objects. It is invisible, just like a magnetic field. Electric field lines are drawn with arrows to show the direction of the electric force. The electric force always points away from positive charges. The electric force always points towards negative charges. The strength of a electric field is related to the distance. The greater the distance, the weaker the electric field. When there are two or more charges, the shape of the electric field of each charge is attracted.st

what is electric force

It is the attraction or repulsion between electric charges.

what is electricity

It is the movement of electrons between atoms. The interaction between electric charges is called electricity.

What is force

The push or pull of an item.

what are electric charges made up of

Tiny particles, that make up atoms in matter.

current in a circut

To produce electric current, charges must flow continuously from one place to another. Current requires an electric circuit, which is a complete unbroken path through which electric charges can flow.

what is an electric current

When electric charges are made to flow through a wire or a similar material. The amount of charge that passes through the wire in a unit of time is the rate of electric current. The unit for rate of current is the ampere (amp or A). The number of amps describes the amount of charge flowing past a given point each second.