ElectrostaticsElectrostaticsCHARGING BY FRICTION CHARGING BY FRICTION

and CONTACT and CONTACT

HTTP://WWW.YOUTUBE.COM/WATCH?V=06K88O1RYSQ

MythbustersMythbusters

RECAP:RECAP:

What is electric charge?What is electric charge?

Where do electric charges come from?Where do electric charges come from?

How can we figure out the charge of How can we figure out the charge of an object?an object?

What is the difference between an What is the difference between an insulator and conductor?insulator and conductor?

CHARGING BY FRICTIONCHARGING BY FRICTION

Charging by frictionCharging by friction: electric charges : electric charges can be transferred by a rubbing action or can be transferred by a rubbing action or frictionfriction

Electrostatic Series:Electrostatic Series:

used to determine the kind of electric used to determine the kind of electric charge produced on each substance when charge produced on each substance when any 2 substances on the list are rubbed any 2 substances on the list are rubbed togethertogether

Electrostatic Series:Electrostatic Series:

the substances the substances higher in the list higher in the list always lose always lose electrons to become electrons to become +vly charged+vly charged

the substances the substances lower in the list lower in the list always gain always gain electrons to become electrons to become –vly charged–vly charged

Rubbing materials does NOT Rubbing materials does NOT create electric charges. It just create electric charges. It just transfers electrons from one transfers electrons from one material to the other.material to the other.

Where do charges Where do charges come from?come from?

When a When a balloonballoon rubs a rubs a piece of wool piece of wool......

Where do charges Where do charges come from?come from?

– Electrons are pulled from the wool to the balloon.

The balloon has more electrons than usual.

+++++

–––––

The balloon: – charged, The wool: +charged

wool

Charging by ContactCharging by Contact

Who has ever touched someone and Who has ever touched someone and got a shock?got a shock?

The difference between charging by The difference between charging by friction and contact is? friction and contact is?

ScenarioScenario

Touching a door knob and a shock Touching a door knob and a shock occursoccurs

Why does the shock happen?Why does the shock happen? What is wrong with this diagram? What is wrong with this diagram?

Charging by ContactCharging by Contact

One object is already charged; the One object is already charged; the other object may or may not be other object may or may not be charged.charged.

There must be a difference in There must be a difference in charge between the 2 objects.charge between the 2 objects.

The 2 objects must either touch, or The 2 objects must either touch, or come close to touching so that the come close to touching so that the charge can ‘jump’ from one object charge can ‘jump’ from one object to another!to another!

Static Electricity in Static Electricity in Winter Winter

At what time in the year does there seem to At what time in the year does there seem to be an increase in the amount of static be an increase in the amount of static electricity? electricity?

Why is that so? Why is that so? Has to do with the air, cold air is much drierHas to do with the air, cold air is much drier Cold air can hold less water than warm air. Cold air can hold less water than warm air. Dry air is an insulator, so it does not take up Dry air is an insulator, so it does not take up

electrons easily from our bodies as air molecules electrons easily from our bodies as air molecules rub against our skin. rub against our skin.

Therefore, the charges that build up on our bodies Therefore, the charges that build up on our bodies aren’t taken away, so we are more charged.aren’t taken away, so we are more charged.

Practice:Practice:

What is charging by friction? What What is charging by friction? What must happen for this to occurmust happen for this to occur

Which electric charges move?Which electric charges move?

How can we figure out the charge of How can we figure out the charge of an object?an object?

What is charging by contact? What are What is charging by contact? What are 2 ways it’s different than charging by 2 ways it’s different than charging by friction?friction?

Discharging Electrically Discharging Electrically Charged ObjectsCharged Objects

Another word to address discharge Another word to address discharge

is to is to neutralize neutralize somethingsomething. This is A.K.A. . This is A.K.A. getting rid of any excess electrical getting rid of any excess electrical charges.charges.

How do we get rid of excess How do we get rid of excess charges? charges?

Discharging Electrically Discharging Electrically Charged ObjectsCharged Objects

What is Grounding? What is Grounding? When a charged object is connected or When a charged object is connected or

grounded to Earth, it shares its charge with grounded to Earth, it shares its charge with the entire Earth.the entire Earth.

For the most part, this effectively removes For the most part, this effectively removes all the excess electrical charge from the all the excess electrical charge from the object.object.

Can you name some important Can you name some important devices that aredevices that are grounded? grounded?

Discharging by Discharging by GroundingGrounding

When a charged object is connected or When a charged object is connected or grounded by a conductor to Earth, it shares grounded by a conductor to Earth, it shares its charge with the entire Earth.its charge with the entire Earth.

For the most part, this effectively removes all For the most part, this effectively removes all the excess electrical charge from the object.the excess electrical charge from the object.

Discharge at point Discharge at point Grounding an object is not always Grounding an object is not always

the best way of getting rid of an the best way of getting rid of an electric charge.electric charge.

The shape of conductors can be The shape of conductors can be used .used .

Conductors pointed at the ends lose Conductors pointed at the ends lose charges rapidly, “discharging at a charges rapidly, “discharging at a point”point” Planes have a lot of these, why?Planes have a lot of these, why?

Discharging at a PointDischarging at a Point

Smooth spherical shapes retain charges Smooth spherical shapes retain charges indefinitely; this is because their charges indefinitely; this is because their charges can spread across their surface evenly.can spread across their surface evenly.

Conductors pointed at the ends lose charges Conductors pointed at the ends lose charges rapidly, because charges at the point (forced rapidly, because charges at the point (forced close together) will repel each other close together) will repel each other

Other Ways to Discharge Other Ways to Discharge Objects Objects

Over a period of time charged Over a period of time charged objects can be discharged by simple objects can be discharged by simple air exposure.air exposure.

On a humid summer day, there is On a humid summer day, there is lots of water in the air.lots of water in the air.

Another way is to simple shine a Another way is to simple shine a light on it, exposing it to light on it, exposing it to radioactivityradioactivity..

LIGHTNINGLIGHTNING

Lightning is a large example of Lightning is a large example of static electricity with a discharge! static electricity with a discharge! How does it work?How does it work?

http://video.nationalgeographic.com/video/kids/forces-of-nature-kids/lightning-101-kids/ 5 min phenomenen http://science.howstuffworks.com/nature/406-discovery-wonders-of-weather-lightning-phenomena-video.htm

Lightning and the bremuda trianglehttp://dsc.discovery.com/tv-shows/curiosity/videos/lightening-strike.htm Lightning safety gov of Canhttp://www.youtube.com/watch?v=7i-ievcMh7k

Upward lightninghttp://dsc.discovery.com/tv-shows/other-shows/videos/other-shows-raging-planet-videos.htm

Nova – lightning 60minhttp://www.youtube.com/watch?v=D2s22BET5Vg

BBC 50 minute version http://www.youtube.com/watch?v=zO6SzfWPPOk

Short videohttp://www.youtube.com/watch?v=RLWIBrweSU8&feature=related

Practice for the QuizPractice for the Quiz