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Electricity. Objectives: 1. Identify two forces that result from electric charges. 2. Explain why objects attract and repel each other. 3. Communicate how positively charged object can be used to determine the charge on another object.

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Objectives: 1. Identify two forces that result from electric charges

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Objectives 1 identify two forces that result from electric charges

Electricity

Objectives: 1. Identify two forces that result from electric charges

2. Explain why objects attract and repel each other.

3. Communicate how positively charged object can be

used to determine the charge on another object.

4. Infer how electric charges behave in everyday

situations


Objectives 1 identify two forces that result from electric charges

Review concerning Charge and Force

Recall that matter is made of atoms which contain

electrons, protons and neutrons.

“ + “charge

PROTONS -

“ – “ charge

ELECTRONS

“NO”charge

NEUTRONS –


Objectives 1 identify two forces that result from electric charges

What do charged particles create?

The positive and negative electric charges in

objects can produce a force between the

objects. If charges are opposite, they will

cause objects to attract to each other. If

charges are alike the will cause objects to

repel or push away from each other.


Objectives 1 identify two forces that result from electric charges

FORCE OF ATTRACTION

“ + “

“ – “

Opposites attract


Objectives 1 identify two forces that result from electric charges

FORCE OF REPULSION

“-”

“-”

Like charges will repel

each other


Objectives 1 identify two forces that result from electric charges

ELECTRIC FIELD

An electric field is a region surrounding

a charged object.

Strongest part of

field is closest to

the charged area

Weakest part of field

Is the area farthest away

from the charged object


Objectives 1 identify two forces that result from electric charges

Perhaps you have experienced this. When you drive

close to a power line you may get some “static” on a car

radio. What causes this?

Power line

Because there is an electric current flowing through

the power line there is an “electric field” around the

line. This electric field can cause “interference” on

your radio.


Objectives 1 identify two forces that result from electric charges

ELECTRICITY AND YOU

Your body uses electric signals to communicate with the brain.

If you touch something hot, the “-” charge inside the nerve cell

changes sending a signal along the nerve cell to the spinal cord,

to your hand, telling it to drop the object.


Objectives 1 identify two forces that result from electric charges

11.2 STATIC ELECTRICITY

Objectives:

1. Identify three ways static charge can build up

2. Explain what causes lightning.

3. Compare electric conductors and insulators

4. Infer why lightning can be dangerous


Objectives 1 identify two forces that result from electric charges

Has this ever happened to you?


Objectives 1 identify two forces that result from electric charges

How does the person who “shocked” you become

“charged” with electricity?

First of all, you must understand that of the three

Particles that make up an atom, ONLY THE –e CAN

MOVE.

When the person who “shocked” you rubbed their

feet on the carpet electrons from the carpet were

moved to the person. This build up of electrons

“jumped” from their finger to your ear.

Static build-up is when electrons become overloaded

on an object. Static means stationary or not moving.


Objectives 1 identify two forces that result from electric charges

In this example the person (object) became

“charged” by

FRICTION

Can you think of other examples of causing

static build-up (charging) by friction?


Objectives 1 identify two forces that result from electric charges

CONDUCTION

Charging by conductionoccurs when electrons are

transferred from one material to another by direct contact

--

-- -- --

When the leaves of the electro-

scope become loaded with electrons

they repel and separate.

  • -

  • -- -

  • ------

-

-

electroscope

  • a device which detects an electrical

  • charge


Objectives 1 identify two forces that result from electric charges

INDUCTION

Charging by induction occurs when charges are

rearranged without direct contact, the charged object

simple comes close to another object.

  • - - - --- --

- - - - -

---

- ---

-----

What has become “charged”?

-

The leaves of the electroscope

electroscope


Objectives 1 identify two forces that result from electric charges

LIGHTNING

HOW DOES IT HAPPEN ?


Objectives 1 identify two forces that result from electric charges

+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+

+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+_+

When clouds are swirled around and blown together by

turbulence in the upper atmosphere, there is a great deal

of friction between the water molecules. This friction

causes electrons to be jarred loose and eventually there

is a build-up of electrons within an area of the cloud.

This is called “static build-up”. When this happens,

lightning can occur in several ways:


Objectives 1 identify two forces that result from electric charges

The most common form of lightning

+ _ + _ + _ + _ + _ + _ + _+ _ + _ + _ + _ + _ + _ + _+_ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _ + _

_ _+_ _ _+_ _+

+_ _ _ _+_ _ _

_ _+ _ _ _+_ _

_ _+ _ _ _ _

++++++++++++++++++++++++++++++++++++

_ _ _ _ _ __ _ __ _ _

One end of the

cloud has more

+ charges.

The other end of the

cloud has more – charges.

The + - attraction between

the ends of the clouds causes

a “static discharge”(lightning)

resulting in a cloud which now

has evenly distributed + & -

charges.

What happens now?

Lightning within a single

cloud is called

“St. Elmo’s Fire”


Objectives 1 identify two forces that result from electric charges

What will happen here?

_ _ _ + _

_ + _ _ _ +

+ _ _ _

_

_ _ _ + _

_ + _ _ _ +

+ _ _ _

_

+ + + _ +

+ _ + + _

_ + + + +

+ _

+ + + _ +

+ _ + + _

_ + + + +

+ _

A charged cloud

A second charged cloud

Where is the + - attraction?

When the negative end of one cloud comes close to

the positive end on another cloud you will see

lightning from one cloud to another.


Objectives 1 identify two forces that result from electric charges

How does one cloud “charge” another?

_ _ _ + _

_ + _ _ _ +

+ _ _ _

_

+ _ + _ + _ + _ + _ + _ + _ + _ + _ + _ +_

_ _ + _ __ + _ _ +_ _ _ +

+ + + _ +

+ _ + + _

_ + + + +

+_ + + +_+_ + +

+ + + +_

+ _

+ _

A charged cloud

A neutral cloud

When a charged object comes close to another object, the

second object becomes charged by __________________.

INDUCTION

What makes this happen?

Like charges repel so when the end with a large number of

electrons (-) comes close to the other cloud the electrons

in the neutral cloud are repelled to the other end of the

cloud causing it to have charged ends.


Objectives 1 identify two forces that result from electric charges

How does lightning strike things on the ground?

What happens?

_ + _ _ _ +_ _ _ _

+ + + _ ++ _ + + +

A charged cloud

+ + + + _+ + _ + +

A neutral

tree with

+ & - scattered

equally throughout

When the cloud gets close to

the tree the tree becomes charged

by induction. When the + / -

attraction becomes great enough

there is a static discharge of

electrons to the tree.

_ __ __ +


Objectives 1 identify two forces that result from electric charges

Why is it unsafe to seek shelter under a tree during a

storm?

Lightning will try to find the

fastest way to the ground. The

people under the tree become

“charged” by induction just like

the tree does. As lightning

takes its path to the ground, it

will come out of the tree and to

the boys then to the ground.

_ + _ _ _ +_ _ _ _

+ + + _ ++ _ + + +

A charged cloud

+ + + _ + +

+ + + _ ++ +

____

+ _

+ _

+ _


Objectives 1 identify two forces that result from electric charges

LIGHTNING

WILL

KILL YOU DEAD!

Don’t make someone cry.


Objectives 1 identify two forces that result from electric charges

CONDUCTORS

INSULATORS

VS


Objectives 1 identify two forces that result from electric charges

CONDUCTORS - A material through which electric charges flow easily.

Examples include most metals such as gold, silver, copper,

aluminum and mercury. Non metals such as water and acid

are also good conductors.

NOTE: Pure water does not conduct electricity, it must

have some type of electrolyte or substance in it. Since the

water you use at home is not pure water, it is a good

conductor, it is wise to be careful when handling appliances

around wet areas.


Objectives 1 identify two forces that result from electric charges

INSULATORS: Materials through which electric charges

cannot move easily.

Examples include wood, ceramic, rubber, glass and plastic.

Note: you may have noticed that most wire to electrical

appliances are coated with rubber or plastic.

insulation

wire

In an insulator, the atoms are not arranged in a manner

which will allow the electrons to move freely. Therefore,

insulators are not capable of carrying electrical energy.


Objectives 1 identify two forces that result from electric charges

SCIENCE AND YOU

Do your clothes ever stick together when you take them of the dryer?

While drying, some clothes pick up a negative charge while

others keep a positive charge.

Using your knowledge about charges what happens?

Does your hair follow the comb or brush instead of lying flat?

Using your knowledge about charges, explain what you

think happens to your hair.


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