Conductors and Conductors and insulators.insulators.

Shocking! Shocking!

If you reach for a If you reach for a metal doorknob after metal doorknob after walking across a walking across a carpet, you might see carpet, you might see a spark.a spark.

The spark is caused The spark is caused by electrons moving by electrons moving from your hand to the from your hand to the doorknob.doorknob.

Conductor! Conductor!

A material in which electrons are able to A material in which electrons are able to move easily is a move easily is a conductorconductor..

The best electrical conductors are metals.The best electrical conductors are metals.

Not a Conductor! Not a Conductor!

A material in which electrons are not able A material in which electrons are not able to move easily is an to move easily is an insulatorinsulator. .

Most plastics are insulatorsMost plastics are insulators

Charging ObjectsCharging Objects

Rubbing two materials together can result Rubbing two materials together can result in a transfer of electrons.in a transfer of electrons.

Then one material is left with a positive Then one material is left with a positive charge and the other with an equal charge and the other with an equal amount of negative charge.amount of negative charge.

The process of transferring charge by The process of transferring charge by touching or rubbing is called touching or rubbing is called charging by charging by contactcontact..

INDUCTION! INDUCTION!

Because electrical forces act at a distance, Because electrical forces act at a distance, charged objects brought near a neutral charged objects brought near a neutral object will cause electrons to rearrange object will cause electrons to rearrange their positions on the neutral object.their positions on the neutral object.

The rearrangement of electrons on a The rearrangement of electrons on a neutral object caused by a nearby charged neutral object caused by a nearby charged object is called object is called charging by inductioncharging by induction..

InductionInduction

The balloon on the The balloon on the left is neutral. The left is neutral. The balloon on the right is balloon on the right is negatively charged. It negatively charged. It produces a positively produces a positively charged area on the charged area on the sleeve by repelling sleeve by repelling electrons.electrons.

Detecting electric chargeDetecting electric charge

When the device is not When the device is not charged, the leaves hang charged, the leaves hang straight down.straight down.

Notice the position of the Notice the position of the leaves on the leaves on the electroscope when they electroscope when they are A uncharged, B are A uncharged, B negatively charged, and negatively charged, and C positively chargedC positively charged

Current and PotentialCurrent and Potential

The net movement of electric charges in a The net movement of electric charges in a single direction is an single direction is an electric currentelectric current..

In a metal wire, or any material, electrons In a metal wire, or any material, electrons are in constant motion in all directions. As are in constant motion in all directions. As a result, there is no net movement of a result, there is no net movement of electrons in one direction.electrons in one direction.

Current and VoltageCurrent and Voltage

When an electric current flows in the wire, When an electric current flows in the wire, electrons continue their random electrons continue their random movement, but they also drift in the movement, but they also drift in the direction that the current flows. direction that the current flows.

Electric current is measured in amperes.Electric current is measured in amperes.

Voltage differenceVoltage difference

In a similar way, electric charge flows from higher In a similar way, electric charge flows from higher voltage to lower voltage.voltage to lower voltage.

A A voltage differencevoltage difference is related to the force that causes is related to the force that causes electric charges to flow. Voltage difference is measured electric charges to flow. Voltage difference is measured in volts.in volts.

Electric CircuitsElectric Circuits

This figure shows an This figure shows an electric current doing electric current doing work by lighting a work by lighting a lightbulb.lightbulb.

A closed path that electric A closed path that electric current follows is a current follows is a circuitcircuit..

If the circuit is broken by If the circuit is broken by removing the battery, or removing the battery, or the lightbulb, or one of the lightbulb, or one of the wires, current will not the wires, current will not flow.flow.

ResistanceResistance As the electrons flow through As the electrons flow through

the filament in a lightbulb, they the filament in a lightbulb, they bump into the metal atoms that bump into the metal atoms that make up the filament.make up the filament.

In these collisions, some of the In these collisions, some of the electrical energy of the electrical energy of the electrons is converted into electrons is converted into thermal energy.thermal energy.

Eventually, the metal filament Eventually, the metal filament becomes hot enough to glow, becomes hot enough to glow, producing radiant energy that producing radiant energy that can light up a dark room.can light up a dark room.

ResistanceResistance